Not too long ago, I switched to screening anonymous comments before they were posted because I was being hammered by spammers who had latched onto one of my long-ago posts about baseball. I still allow anonymous comments, largely for the convenience of one of my good friends who does not have an LJ.
Unsigned, unsupported anonymous comments from people who simply feel moved to disagree with me will be consigned to the bit bucket. If your opinion is that much more valid than mine, then the least you can do is sign your name. When I comment on other blogs, I use my real name, not even a recognizable handle. I, at least, have the courage of my convictions.
And if I get tired enough of anonymous drive-bys, I can always disable anonymous comments altogether.
My good friend will just send me an e-mail. :)