I agree that it is not a fallacy to use a counterexample to refute a universal claim. That's why I said "[reasons are] sufficient to justify the car, ... in the cases at issue." The fallacy appears when the refuted universal is taken as a universal refutation. That is, if you refute "nobody has sufficient reason to drive an SUV" you get "Somebody has..." (i.e. the farmer) rather than "everybody has..." (the farmer and the City banker). My concern is about the banker who keeps talking about the farmer, in trying argue that the banker's SUV is legitimate.

@Josiah So in your scenario the banker is arguing this in the context of some proposed bill or policy to prevent the banker from driving an SUV? Well, does the bill make an exception for the farmer and everybody else who has or might have a genuine need for an SUV? If not, the banker has a valid point against the bill.

Suppose the current version of the bill has no carve outs, and he gets to choose whether to try and amend it (to add the farmers exception) or to try to block it. If he would choose to amend it, he's clearly reasoning correctly and in good faith. That's not the sort of case I'm considering. The cases I'm considering would always use the farmer example to block the whole bill, because it wasn't about the farmer in the first place. I tried to make that clear in the symbolic version of the structure.

@Josiah It is not necessarily the case that the best thing to do with the bill is amend it to add the farmer exception. Because, the farmer is just one example. There may be many other sympathetic examples, too many and diverse to enumerate in the bill. Perhaps the enforcement effort of determining whether someone has a legitimate need for an SUV is too invasive and expensive. And there may be other good reasons to reject the bill. So it is not the case that just because the banker points out one flaw in the bill, he is obligated to back a version of the bill without that particular flaw.

Rather, once the banker has pointed out the flaw (and if it is generally agreed that this is a bad enough flaw) the onus would then be on those who propose the bill to produce a better version of it. Which the banker may still have other legitimate objections to.

I'm getting rather confused as to why you're arguing this point. I'm giving illustrations as an intuitive aid for where this sort of thing comes up, but you seem to want a formal proof that the illustrations couldn't be rewritten to describe good logic. If I'd asked "What's the fallacy where people say 'murder is wrong because Einstein said so'?" you presumably wouldn't reply "Not a fallacy. There can be valid reasons to quote other people, such as quoting the Supreme Court to know if something is legal."

Suppose I, with full knowledge of my own mind and intentions, know that my case is squarely within the uncomplicated zone and the only reason I don't like it is that it's against my own interests. I know strategically that my best chance of protecting my interests is talk about protecting a more sympathetic third party. What is the fallacy involved when I say "What about the farmer?" or "Think of the children!" or such when trying to get to "Let Josiah do what he wants."?

@Josiah Even if you are motivated by pure selfishness, it is still possible to make rational arguments about whether the bill should be passed. To say a person's arguments are wrong because they are only being selfish (even if they are only being selfish) would be to commit the ad hominem fallacy. Anyway, I think the usual case where this argument actually comes up is in political discourse where one publication raises an unsympathetic case and another publication counters with a sympathetic case, both arguing on different sides of some policy. It's not fallacious there.

@Josiah although really both sides should be talking about population statistics and net harm/net benefit calculations instead of individual cases. However, that doesn't make for attention-grabbing news stories.