What’s the difference between Nazis marching around, throwing their arms up and other protests? Intent is very important, it can completely undermine your society. And there is no way to let religion in without it getting its tentacles into all aspects of your society, just like authoritarianism. Thats why other cultures banned missionaries back in the day.
Because, before you know it, they’re telling you how to run your government, telling you what laws to enact, and stripping away your culture.