I've made the same allowance for a visitor to a forum I run. He is incredibly abrasive and snarky in general (especially when people disagree with him, however

I've made the same allowance for a visitor to a forum I run. He is incredibly abrasive and snarky in general (especially when people disagree with him, however politely) and vain about his own writing, which is mediocre but he refers to as "truly insightful" and "a cogent analysis of this subject". It consists mainly of densely-worded diatribes and conspiracy theories, with scattered "photoshops" of politicians he dislikes (which is all of them - nobody is good enough for this guy). It's truly disturbing, in the way that observing another's emotional turmoil can be. Mainly I try to leave him alone.