Comment on Policy opinion: am i going to suppress the freedom of speech if i ban religion topics and porn on my instance?

I think "suppress the freedom of speech" is a sort of clumsily applied term here. What you're trying to implement are effective house rules and I really don't see anything wrong with that. Without simple rules like that, people could just hop into your space and be abusive assholes then claim "FrEe SpeEcH". I'd say go right ahead and do what makes you feel comfortable.