You know, I used to be a really angry guy. It got to the point where instead of surprise or disappointment or even sadness, I would get angry. I also found that I could use anger to fuel things like creativity and productivity. Of course, all of this came at a cost. While most people I interacted with knew that I was a pretty nice guy, sometimes they would tiptoe around me trying to make sure I didn't get mad. This had a marked effect on my relationships.
The point is, repeated actions have a way of becoming automatic. Trolls or people who say horrible shit on the internet because they feel like they can get away with it are training themselves to think that this behavior is acceptable, not only on the internet but in real life, even if they only express these behaviors internally or to select people. I don't believe in policing the internet or forums, but I do think that this article touches on a really serious issue that will only get worse if people stay dismissive about it. The reason labels are so dangerous is that they are dehumanizing. They create a caricature of the behavior that allows people to rationalize away any number of things. I think that at this point, at least in Western civilization, we should all be aware of the fact that as humans we're not good at seeing the big picture and that small things contribute to bigger things.
I too used to troll people, but this was more than 15 years ago. I did it because it made me powerful being able to affect someone I had never met and likely never would meet. Some people branded as trolls really are kids and it's likely that most of them will grow out of it. However, if there is an internet climate where this is increasingly OK and where adults are doing it, then I don't think that's OK, that's a sign of something deeper that needs to be addressed.