This is an interesting answer in the context of France. Catholicism has (almost always) been the state religion for centuries, until the Revolution (then various things happened) and reaffirmed in 1905. So France, officially, is not pro-religion (a lot of things happening in the US are not conceivable here), religion still gets a favorable treatment in ant-discrimination laws.

@WoJ Like the rest of Europe, France has some pretty vicious religious conflicts in its past: The French Wars of Religion were a prolonged period of war and popular unrest between Roman Catholics and Huguenots (Reformed/Calvinist Protestants) in the Kingdom of France between 1562 and 1598. It is estimated that three million people perished in this period from violence, famine, or disease in what is considered the second deadliest religious war in European history (surpassed only by the Thirty Years' War, which took eight million lives).

@HopelessN00b: oh yes, absolutely. But today it is a secular country, still retaining this special treatment to religion (in the context of the OP question, including counter examples like flat-eath believers)

Are you saying religious persecution only happens in the past? Only if the past is 2017. In the US.

@DJClayworth no argument, but that is noteworthy in 2017 in a way it wasn't in 1617. Hence (I think) the OP's confusion.

"they prevent a powerful religion from oppressing members of a less powerful faith." So? My rival Call of Duty clan is more powerful than mine, should we put laws in place that affect people who don't play Call of duty to prevent that from happening? Of course we shouldn't. (disclaimer: I don't actually play Call of Duty)

@EdmundReed We should the moment Call of Duty is an import enough aspect of life for a large enough group of people that people who don't play it are invariably affected by what happens during the CoD games.

@DonFusili but we are enabling such large numbers by by affording them special treatment. Without this enablement, which would also be supported by large numbers of people, perhaps the numbers would reduce to the extent that they would no longer affect others. It's basically a case of "the rich get richer".

@EdmundReed substitute "culture" for religion and the point still holds.

@JaredSmith the point holds if the assumption of it being based on a large enough group of people is a fair parameter on which to afford benefits. There may be other reasons to afford benefits to people because of their culture that shouldn't also apply to religious groups, such as supporting your economy by buying local produce instead of imported goods.

@EdmundReed I'm somewhat of the opinion that people should not be persecuted for their choices (to the extent that they don't harm others), at all. Ever. Even flat-earthers. I'm definitely of the opinion that people should not be persecuted for their innate qualities. To the extent the two are in conflict (e.g. one chooses to be in the Westboro Baptist Church) the latter wins, but the former is still valuable in itself, on principle.

"decided to prohibit the government from persecuting religions." I would like to add that the American civil war effectively pushed this same restriction onto individual states, and then the civil rights movement pushed this restriction onto individual citizens.

@NicHartley You kind of hinted at it in your comment, but by private citizen I mean that as a person engaging in commerce (employee or business owner), you are prohibited from mistreating (ie to persecute, discriminate) based on a person's religion. Prior to the civil rights act, restrictions of this kind were only on governments, government employees, and elected officials.

Correction: The Puritans were not so much fleeing government religious persecution, but seeking a place where they could a) escape retribution for their past persecutions of others (see e.g. Oliver Cromwell & the English Civil War), and b) do their own persecuting.

@jamesqf I think not: the initial Puritan migrations were 1620-1630. The bulk of them came over from 1630-1640. They didn't gain power in England until the late 1640's. See this and this for reference.

@jaredsmith Sorry, no. The puritans that fled persecution in England initially fled to the Netherlands, which was famously tolerant towards all religions -- but then they discovered that it meant they'd have to tolerate other religions as well, so they went across the atlantic to find a place they could make for themselves where they could be comfortably unpersecuted and intolerant without comment.

@Shadur I wasn't there, so I checked wikipedia. Could you please add a source? I've updated my answer with a reference to your comment.

I can write a rule that would have always worked to categorize real religion from a bogus claim to get away with something. The rule requires being read forwards from its starting point to reach its decision rather than starting from the wanted conclusion and being read backwards to find a path to get there.

@Joshua no offence, but I'm skeptical of anyone claiming they have a deterministic algorithm to answer a nuanced question with complicated inputs (see also e.g. whether or not Pluto constitutes a planet, whether or not a transgender man constitutes a man, whether or not a virus is 'alive', etc.). Care to elaborate?

@JaredSmith: Approximately: The religious claim that is in conflict with the law has to have a chain of evidence of existence such that it could have been discovered by lawmakers before writing the law. If I wasn't dealing with lawyers I would write "could have reasonably been", but lawyers have a different definition of reasonably than engineers. This is still full of holes, the hole-free version would run several paragraphs.

@JaredSmith: Yes, and that's intentional. There is a designed way to escape that, but it's too large for a comment.

It might be a good question for history but I think that this had more to do with creating a cohesive nation and the fact that the founding fathers such as Jefferson held views that were essentially heretical. In addition we tend to forget how non-united the colonies were. If Maryland persecuted protestants and Virginia persecuted catholics, the idea of free movement across state borders would be impractical. The elites of Virginia did not consider the Puritans part of their history.

It might be interesting to add some examples of countries where religion is not protected and how that has created all kinds of persecution of religious groups.