The issue is that everyone has a different perspective on what constitutes "trolling" and what doesn't. These "civil forums" frequently develop a habit of banning anyone who tries to do anything other than shout more echos into the echo chamber on the pretext that they're "trolls" or otherwise unsavory community members. A policy that encourages such casual non-concern for participants is likely to result in some very one-sided outcomes.
Sorry, I don't think that's an accurate reflection of online social dynamics. Echo chambers certainly exist and I've run into that same problem myself, but I managed to disagree without disputing other people's freedom to participate in such forums, doxxing people, making death threats, or engaging in any of the other activities that obnoxious trolls are well-known for.
