We all have our own intolerances. My own is of people who take the idea that Science doesn't know all the answers (correct) to mean that they can justify all sorts of weird and completely nonsensical ideas about how the world works. Two examples that spring to mind immediately are homeopathy (it's just water or sugar, people!) and Young-Earth Creationism. Well, Creationism of any form really, but particularly that which requires the World, and the Universe, to be young. Nothing supports it at all.
In general I try to be tolerant or respectful of people's opinions if (I think) there is any scope for doubt, and perhaps am too tolerant of some views as a result and not tolerant enough of others. I don't think I get the balance right but hopefully I will eventually.