Not only is it the most effective way to annoy them - nothing is more irritating to a fisherman than when a finely-baited hook fails to generate a nibble - there are a subset of trolls who - quite literally - get off on the abuse you fling at them.

So if you want to visualize some overweight kid in a grungy white t-shirt staring enraptured by your words, giggling and fondling himself while a line of spittle dribbles down their chin... hey more power to you, different strokes for different folks. Personally, I think that's just gross.

Note there is a significant difference between this and the your-silence-is-unspoken-support that bigots feel when they spout off bullshit and no one calls them to task. Trolls aren't looking for your *support*, either overt or covert. They're looking for your *reaction* - and even playing along gets them what they want as it keeps the tread going.