SPAM has a clear definition, and I don't think you will find anyone anywhere who disagrees that it needs to be blocked.

But "troll" is hard to put an objective lid on. If I try to argue science to antivaxxers I may be labeled a troll. If I try to oppose HTML DRM because I believe it's bad for the internet, some people will label me a troll for that.

If I enter a Muslim internet forum and insist that Muhammed was a pedophile, I may have my facts straight, but it will be hard to argue that I'm anything but trolling.

So where do you draw the line on troll? Who decides what troll can be censored? This sounds extremely shady, and if I may raise the conspiracy flag, intentionally open to interpretation.