'Trolling' is merely casting out bait to catch the unwary isn't it? 'Bait', in most cases, is nothing more than a slur that can be either blatantly obvious or of a more subtle nature. As long as it isn't too heavy handed it can be a good way to get a reaction and to start a discussion off.
Another term I see bandied about as a label for trouble makers (especially on forums) is that of being a 'WUM' (wind up merchant). Again these exhibit similar tactics in that they load their replies with personal insults be it only slightly at times - just enough for readers to take it personally should they wish. Again it can be used to good effect.
I will say that anyone who takes part in any discussion where they lose their cool or becomes agitated in some way will lose the battle - argument - whatever against such people. It is what they thrive on. It is the whole reason for the goading. They are argument junkies who get high off other peoples rattled reactions. Very difficult not to become upset when faced with either. It generally takes one to spot one.
Dealing with the irrational? Discourse should get through eventually as long as they can calm down sufficiently. Once they take solace in rage there is no way through though. They have to be disarmed in some way first and brought back to reality.
Of course to change the mind of someone you have to have the most potent points at your disposal in the first place else it will be you left looking foolish .