This is a very different website from youtube, where all trolls, without exception, are bad. This is a site made for submitting art, not videos. Most of this stuff is protected by copyright. And some people steal other people's art and claim it as their own, a serious violation of DA's rules, which I think is a bigger problem than trolling.
Yes, the bad trolls are certainly jerks who do not deserve to be on here. But DA's few admins can't possibly administer such a large website and protect every single user from art thieves. And on a site that is rampant with users who steal other users' art, who is going to protect the rights of the artists?
The answer: The Good Trolls. The ones who don't just bully people for fun and instead use their abilities of trolling to fight for artists whose work has been illegally stolen.
So please don't lump all the trolls into one category.