Nothing takes the wind out of even the wittiest, most biting critical comment as swiftly and decisively as the appension of a "lol." (Try it.)
Surely no man, no mortal creature, is more invulnerable to judgment than when he is faced with the lolling (or depending on your regional dialect, lawling) troll. It is too hard. This is, after all, someone who cannot converse without convulsing with glee -- a sign of a simpleton -- essentially unable to resist laughing at his very own words.
I find it comforting that although it is the online space that spawned and enabled them, it is what again cripples them. This is satisfaction -- that of a responsible parent who takes care to shush their own brattish children.