I don't know the person under discussion other than seeing him occasionally mentioned on this site, so I have no basis for an opinion about him, but speaking ge

I don't know the person under discussion other than seeing him occasionally mentioned on this site, so I have no basis for an opinion about him, but speaking generally, being a jerk doesn't mean some has to treat _everyone_ poorly; sometimes being a jerk to only some people is still enough to qualify someone as a jerk. As a made up example, a boss who plays favorites by letting their cronies get away with being lazy or not following rules but makes trouble for anyone outside their inner who slips up even slightly is a jerk, even though they don't act like one to their favored few (who would probably protest vigorously at the suggestion that their boss is a jerk).