I'm on one forum where the only rules are "leave family other than spouses out of it" and "no n-word". It is a hobby interest forum with a gender homogeneous user base. It's one of the most civil places on the internet if you can get past the fact that any mistake will be remembered and you will be made fun of for it. There are definitely some people who hate each other over ideological differences but they seem to tire of arguing and just ignore each other. I think small enough group size for people to remember each other and no reason for people without the shared interest to stick around matter more than anything else.