I'd like to think that threads I've killed were either because they were going to die anyway, or because I made such a convincing argument that others realized there just wasn't anything more to say.
However, I suspect that others may have been thinking, "this guy's a jerk, but I don't feel like arguing with him."
Lately, I've actually tried to stick to the lighter subjects and areas like the Lounge. I'm trying to stay away from getting into confrontations, but every now and then I get sucked into one of the dead horse threads.
There is a poster here (not in this thread yet) who argues very well, and usually takes the exact opposite position of me on a lot of issues. I put him on my ignore list just so he wouldn't set me off.