Just remember that he's probably a pathetic little loser who hasn't had a shag in years and he'll probably end up a very lonely and disliked old man.
Whenever I see posts about these cruel trolls, I always think about how sad it is that this is how they choose to spend their own time/their lives.
Their peers are out in the world making money, making friends, socializing, dating, doing things. Passing them by. And by comparison, what are they accomplishing? They’re wasting their years online, hurling insults at strangers.
And as you mentioned, anyone who is like this online probably has a hard time being pleasant in the outside world, too. Probably not many friends as a result (and the ones they have probably discuss what a dick the guy is when he’s not around… or they’re the same way, which means he also gets treated like shit by the only people he actually likes).
So keep that in mind, too. When you log off, you can be rid of that guy’s negativity. But he’ll have to endure it forever. He can’t escape it. You win!