To me the fact that "trolling" means different things to different people should be enough to render questions on it moot. What I call trolling is playing devils advocate and taking extreme counter-positions to make someone "bite", and isn't really harassment or bullying.

But it's a fine line, and in the end you have to decide whether you're ok under free speech with someone taking the "Hitler was a net positive" position [on a Jewish dating site] or if that's a form of harassment.