Comment by ViscountPenguin

I'm relatively confident that the US Constitution doesn't contain any prohibitions against the private boycott of people with different religious beliefs.

I've thought about it a fair bit, and I don't think there's really a very clear line between which religious beliefs people should politely decline to comment on, vs openly critisise. The cultural taboo that exists in much of the west against privately excluding people on the basis of religion has had some really positive effects (the marked decrease in religious violence of the past few hundred years is amazing), but it also leaves society somewhat vulnerable to the spread of some particularly cancerous ideas.