Being disruptive is a perfectly good reason to give someone a warning/tip on how they can not do that. Banning them without warnings and/or discussion is generally not a good idea, unless it is blatantly obvious that they have no intention other than to troll.

This is not a very specific community site, from what I can gather, so that first rule should be only expected to reasonable amounts, depending on the specific forum categories for those things.

I believe to solve a lot of the problems with disruptive or unwanted members would be the ability to hide a person from appearing, if you so wish, so that people you have no interest in communicating with can be hidden or blocked or whatever. Because otherwise, their friends will get all angry and stuff, even though they did the wrong thing. I think hidden or blocked people should still be able to send PMs and stuff, but with the person marked as blocked/muted/hidden, so that you can decide whether you do or don't want to read it. If there is a member that didn't intend to do you any wrong, it would be bad if there was no way for them to apologize or whatever.

That's my thoughts on all this stuff and things.