If you're ever going to listen to anyone, you should know to listen to people who have been supportive in the past.
Yes, there will be people who are always critical of you no matter what you do or say and it's reasonable to say you don't need to listen to them and can ignore their views.
But someone who has supported you? They are not your enemy, they are telling you something, that you've taken a wrong turn or gone off the rails.
That's the time to stop, listen and be humble.
But of course he doesn't do "listen" or "humble". He simply switches that person into the "anti-me" column and declares them the enemy.
He was able to build support because there was a ready, waiting, eager audience. He's reached the point where he alienates people faster than he can gain new viewers. The low-hanging fruit are all gone and he's built walls so high he can't see new trees anymore.