well one thing you will find in atheist communities is of the major religions left in this world Islam by in large is frowned upon the most. However, large parts of Africa are starting to radicalize Christianity and are starting to catch up so its important to stay on top of these things. They are burning "witches" out there which is something that is not really talked about these days. I think extremism is probably fine but I think there is a difference in radicalization. Like an amish person is an extreme Christian there some extreme muslims that are peaceful radicals are a different story that's when things start to get violent. In America though extreme Christians are pretty harmless imho.