Wait, I think I may have a solution!
A vexed question, I fear.
(a) if we were to eliminate those whom we might think to be inferior, the forum would become unashamedly elitist.
Would that be a useful end ?
(b) if we turned our backs (hypothetically, as the owners would not permit that to occur) anarchy would ensue.
Definitely not useful.
(c) what we endeavour to do is
(i) keep the absolute ratbags at bay, having given them time to demonstrate their extremism
(ii) keep overt nastiness at bay, per the generic Rules of Engagement
(iii) try to keep threads on a reasonably even keel without exercising moderator bias or being precious
Do we succeed ? Not too sure. But that's about as good as we can do, I guess.
Safe aviating.