I think the fundamental issue is social communication without any social consequences. In real life if you continually insult and troll people, you will be a pariah. Online, you can find others who admire and support that behavior. And all you need is another anonymous/pseudonymous account to keep doing it if you get blocked.

And no, that does not mean that I am calling for identification. It just seems to be a natural consequence of having social interaction without real consequences.