The funny thing is, that is just what many you would call a "troll" do, and it can be hard to tell the difference - at first. What makes a troll a troll, is their intention in doing that. I like to debate issues, it's a good way to get yourself and others to really think about things - a troll simply delights in pissing people off, and the classic troll may start out with something resembling a debate, but will soon degenerate into name-calling.
And that, for me, signals end of discussion. It can be hard to resist, as I often have more to say, more reasoned arguments and refutations, but once the word 'moron' hits my screen you are officially no longer worthy or capable of participating in the discussion.