"Until recently a wall was seen to be only a talking point, rather than a serious solution to address the underlying problem"; This is not correct. Discussions of a physical barrier along the US/Mexico border go all the way back to at least the 1980s. Long sections of fencing were constructed in the 1990s, and Congress even passed the Secure Fence Act in 2006. The only thing that's changed is that the word "wall" is now being used to describe it.

@WesSayeed along sections of the border, not along the entire border which parts of it are owned by parities that have treaties with the government saying that they have control of it instead of the government.

@WesSayeed Swapped that part with clearer, more explicit language. Thanks for the feedback.

@Peter: To the methods of drug smuggling which render the Wall irrelevant you could add airplanes, cargo ships, purpose-build submarines en.wikipedia.org/wiki/Narco-submarine and for all I know, drones. Of course most of those could be used for humans, too. And of course there's the great extent to which US drug prohibition has, by causing the growth of cartels &c, encouraged many Latin Americans to come to the US as an escape.

@jamesqf those are not profitable for most human trafficking. They work for drugs because that can be sold very lucratively in the US. Human trafficking works on the principle than many people pay a relatively small amount of money. A rich person may be willing to pay something in the tens of thousands$. That works out to less than a grand per kilogram of 'goods'. A kilogram of cocaine goes for 50K wholesale. And cocaine requires much less attention (drinking, feeding, etc.)

re: "Until recently, a continuous physical barrier along the entire USA-Mexico border was not widely discussed as a realistic solution to an actual problem at the border." This is not true. In fact, it was so widely discussed from time to time that the memes about it existed in the popular culture. George Lopez not only made a popular joke about it (a la "if you deport all the Mexicans, then who is gonna build it?"), but he was also accused of stealing the joke as far back as 2010 (lasvegassun.com/vegasdeluxe/2010/jun/24/…).

This answer seems to promise some claims without delivering. For example "People on different sides of the divide fill in the blanks differently, so they end up with different conclusions." is a nice beginning; but I only see the answer discussing how the pro-wall side "fills in the blanks". As a second example, "not a single one is true.*" is asserted and then, following the asterisk, we find weaker claims like "there is no basis to assume [one of the statements is true]".

A wall would stop small drug traffickers- they don't have the resources to dig tunnels or contacts to use current one or any other equipment other than a few trucks.

This answer would need sources to prove that the main concern against the wall is that it would not be effective enough. Because in the left-leaning media and forums, the arguments against the wall seem to be overwhelmingly "no one is illegal", "everyone is welcome", "all Republicans are all racists!", "whites are evil and we should make them become a minority", and so on. Whether these opinions are really the majority among the opponents of the wall, or merely the loudest, I don't know. But this answer assumes most opponents of the wall are only concerned about its inefficiency.

@vsz To summarize your comment: Strawman&lie. Lie. Lie. Lie. Lie. Lie. Strawman. Lie.

@Hasse1987 1) The answer doesn't discuss how either side "fills in the blanks", I do not know why you think it does so. 2) You object to the claim "there is no basis to assume ", because you failed to realize it isn't a claim. It's a conclusion based on the strong claim - backed by 4 linked sources - that smugglers already use a multitude of methods that would be entirely unaffected by a hypotherical wall.

@Peter 1) Your first sentence and "tl;dr" asserts that different sides fill in the blanks differently. So if, as you say, the answer doesn't discuss that, then you haven't established what you claim. More importantly, you are currently answering the question "Why does the pro-wall side wrongly support building a wall?" not the balanced question "Why is a wall a polarising issue?". 2) No. Whether it is a "claim" or as you say a "conclusion", the assertion "There is no basis to assume X" is not the same as "X is not true".

@JJJ: First, I clearly stated that those methods referred to DRUG smuggling, #2 of the three implied falsehoods. However, I note that we see from current European experience that ships are a viable method of transporting woould-be illegal immigrants, and many do come to the US via airplane, simply overstaying a tourist or student visa.

@Peter That well-funded drug cartels will still find ways to get in does not prove that the vast majority of illegal immigrants - who are not drug smugglers and don't have the resources to construct elaborate tunnels under the border - would be able to get in. Additionally, your 'proof' (which is no proof at all, but just your opinion) is completely ignoring the very basic principle upon which all security is based: make the other person's objective more difficult and expensive to accomplish. Showing that it's not impossible to cross does not show that it won't significantly affect security.

@Peter Your argument is like saying that there's no reason to password-protect your computer because the NSA or Chinese military intelligence can probably still hack it. In short, it's nonsense that literally no one actually believes, regardless of what they might say.

@reirab The answer mentioned tunnels while debunking claim 2). It did not mention tunnels to debunk claim 3). Your claim that tunnels are unlikely to be relevant in claim 3) is nice, but doesn't relate to anything I wrote.

@jamesqf distances in Europe are much smaller. The only short distance from the US to mexico is along the border which is a relatively small spot to guard. In Northern Africa there are many places to depart and land in Europe.

@reirab "Showing that it's not impossible to cross does not show that it won't significantly affect security." - Correct. But just like your other comment this one again fails to address what I wrote. I showed that it's trivial to cross, and that it's trivial to smuggle drugs, even if a wall is built. I did not at all mention how a wall "affects security". Before that we'd need to figure out what "affects security" actually means, which brings us back to the core of this answer: there is no statement on record telling anyone what the wall is actually supposed to achieve.

@Peter You neither showed that it's trivial to cross, nor that it's trivial to smuggle. You'll find that a ladder or rope doesn't help you much against razor wire at the top. And, even if that can be dealt with (it can be,) you seem to be assume that a wall would be unpatrolled, which is a very poor assumption and contrary to pretty much any border defense ever devised. Walls slow people down so that whoever is defending the wall can have a chance to detect and stop them. Or else force them to use a more expensive and/or risky means (such as the tunnels, airplanes, etc. that you mentioned.)

@reirab "You'll find that a ladder or rope doesn't help you much against razor wire at the top" Cool, now the hypothetical, illusory, ever changing wall has razor wire on top. I stand corrected: A ladder and a blanket.

@Peter I was using 'security' in the broad sense of the word, referring to all security. Security is the whole point of any wall that's intended to stop people or animals. You're ignoring the very basic principle that applies to any form of security whatsoever: that your goal is to make your adversary's job more difficult, not to make it impossible. Whether you're defending your house, an international border, a computer, or a classified document, your job is to find an efficient way to make their job harder, ideally to the point that it's not worth their time or effort.

@reirab We were talking about boat migrants, I don't think crossing by boat into El Paso is a viable option. The only other option is Cuba to Florida, but then you need to go to Cuba first.

@JJJ Ah, gotcha. Sorry, I missed that context. That makes much more sense.

@Peter Wow, so you've never seen articles stating that wanting to stop illegal immigration is a bad thing, and you've never seen articles claiming that the proponents of the wall are wanting it out of racism? Never ever? It's strange to call me a liar just because I mentioned their existence which you can confirm by a 5 minute google search. You also skipped over my comment about me not knowing whether such views are a majority among opponents of the wall, or just a very loud minority. Ignoring that makes it easier to call me a strawman. Still, you failed to produce evidence for your claim.

@vsz It's amazing how you moved the goal posts from "the arguments against the wall seem to be overwhelmingly" to "you've never ever seen a single example of this?". Although admittedly you already backpedaled one sentence after making the claim, so I guess there's precedent.

@Voo : I didn't backpedal from anywhere. I was just accused of lying, in very rude way, and was answering that accusation. You ingeniously missed my statement "Whether these opinions are really the majority among the opponents of the wall, or merely the loudest, I don't know". That was part of the comment. Backpedaling is the tactic of making a big claim, and if refuted, retreating to a smaller claim. As I wasn't refuted before writing that sentence, there is no need to backpedal, is it? Still the burden of proof is on the answerer, not on the one who pointed out a gap in the answer.

@vsz You made the claim how in "left-leaning media and forums" the arguments are overwhelmingly of that kind and then made a non related statement about all proponents. Two very different sets of people so the latter statement doesn't refute the former (if it did why make a statement that you take back a sentence later? That'd be rather pointless). Now you're not arguing anymore that the vast majority of leftwing forum and media posts argues that, just that Peter surely read at least one. So that's backpedaling right there.

@vsz Consider linking to some of them, just for the sake of argument.

To back up that the third implication is false (the wall would be ineffective), I would link to this commentary by the Cato Institute, a libertarian think tank.

@Daniel Thanks for the additional information. I'd like to emphasis that my main point is that we don't even know what The Wall supposed to do, and are therefore in a bad position to judge if it does it effectively. Therefore there is a need to be specific when saying what a wall is ineffective at: Stopping or significantly hampering smuggling and stopping or significantly hampering illegal immigration. And I'm not using these points as arguments against the wall, but to demonstrate how implied statements about the wall by its proponents are often falsehoods, which lead to its divisiveness.

I'd move all these comments to a chat if I was admin - so many have nothing to do with the actual answer.

This comments section is a perfect illustration of "People on different sides of the divide fill in the blanks differently... any attempt to dive into the facts of the wall discussion will fail before it starts"