Politics and name-calling aside, there are instances where running AV on UNIX is the preferred technique for protecting Windows machines. It's been stated quite a few times in this thread (and countless others), but I'll state it once more:
everyone said:
Windows was designed to allow others to run code on your machine...Linux was NOT designed that way!
This is the root cause of the need for AV on Windows. Plain and simple. (If you've never messed with writing code to control a Windows box (mouse and keyboard), I recommend you try it...then try porting your program to Linux... see what I mean?). It's fairly easy to control many aspects of a Windows machine (keyboard and mouse are just visual ones...there are many others), but accomplishing the same on Linux is quite a bit tougher. Linux doesn't take well to auto-run code and the like, but that doesn't make it *secure*. Linux users still need to be aware of rootkits and trojans.
No, running AV to protect a *nix box isn't recommended...but if you're the paranoid type, check out chkrootkit and rkhunter (programs to hunt down rootkits on UNIX machines). You'll get a LOT more good out of those two than (insert your favorite UNIX AV).