What is basic decency? Is it indecent to advocate for atheism or if a women posts a picture of herself not wearing a burka? Many people in certain countries would say so. Personally I think those people are insane, and that maximal freedom of expression is the most important human right, but the fundamental problem is that there is no consensus on what constitutes basic decency.

I'm not talking about cultural differences. I'm talking about people simply being assholes online. You will always have a group of people complaining about the rules, that is inevitable.

You're correct that decency is a nicer word for conformity. Preventing social discord avoids violence, but creates repression. I think the compromise is basically liberalism. Let people make their own communities. Let people switch communities, criticize other ones non-violently, enforce their own w/ democratically determined rules, etc.