I agree with a lot of what you said about this Fire, but I think I disagree in not having a line or limit involved. From what I'm gathering from your posts you're for full on "let everyone bang" forums or discussion in general. Is this correct?
I think very few people should be banned, silenced, blacklisted, etc, except when they are blatant in the way you described this friend of yours. The counter I would say to that is if you are allowing someone(s) a large platform to spread, lets say racism as an example, then the potential for them to sway people is larger. That Greoric or whatever his name was comes to mind. He was very intelligent, but used his intelligence to argue from a scientific position why white people were vastly superior to minorities, how racism is normal, and even preferred. This type of person may go to "darker corners" after being banned, but would they really have not taken that route eventually anyway? I doubt it. Only difference is they aren't here to wrongly influence others.
I think there is a line between what should be allowed on any platform vs what shouldn't be, and things/people that tend to get banned from discussion forums usually cross that line.