I haven't been online since Friday, so I'm just seeing this thread and haven't read anything beyond the first page.
I posted on, and was banned from, ZZLP. I also simply read ZZLP, so I saw several of bannings happen in real-time. Some were warranted due to threats, profanity, personal attacks, etc. Many were confusing. One example of a confusing ban was that of a long-time internet poster - CincyDawg. I've posted on 3 different forums with him and he is the most (sometimes frustratingly) benign posted I've ever encountered. Rarely replies to another post. Has never, as far as I can tell, threatened anyone, used profanity, personally attacked yet he was banned from ZZLP. The reasoning, as far as I can tell, was because his middle of the road-ness got other posters all wound up.
ZZLP, IMO, had a very specific view of how they wanted the forum to run....and it was with strict guardrails. People who were persistent with non-liberal views were often labeled as trolls and shown the door. Bringing up race (non-white) was "at your own risk", even if what you were saying was factually accurate. My last banning, I believe, was because I said (paraphrasing) "I'm all for ensuring equal rights for LGBTQ people but I don't think we should be 'celebrating' what is ultimately an abnormality any more than we should celebrate autism."