Normally, the right thing to do with a troll is ignore him. (Pretty much always a "him" rather than a "her," and it's a good bet that it's a "him" who doesn't have a girlfriend.)
If you give feedback and attention to a troll, he'll come back for more with even nastier abuse and less to contribute to a meaningful conversation. Having suffered a bit of trolling myself over at LOOG, not responding was something of an effort of will because ignoring someone who taunts you is frustrating. But the rule, and it's a wise one, is "Do Not Feed The Trolls."
I put up with some hostile comments here, if the commenter has something substantive to say within even a generally abusive message. Content-free invective is subject to censorship by me through the deletion of comments, and if repeated, bannination from the site. I try to tell those with hot tempers when they are approaching the line in comments, and that generally seems to work; I've not banned anyone and I haven't deleted a comment (other than true spam) for at least eighteen months now.
So just in time to cheer me up after trolling on my cross-post, Radley Balko found another way. He fed his troll. He fed his troll notes. Whether you agree with Balko's politics or not, this evisceration of a troll is nine out of the ten kinds of awesome. (He misses only on Awesome #7, "Sexually Arousing.")