"Apple encourages the widespread use of multiple antivirus utilities so that virus programmers have more than one program to circumvent, thus making the whole virus writing process more difficult."
The original support page, which was available here, and has since been pulled, went on to recommend common Apple anti-malware applications such as Norton Anti-Virus and Intego VirusBarrier. (After trying both, I prefer Intego. I also use Intego's firewall because I just don't feel like messing with the firewall command line to change policies.)
Turns out, according to TUAW, the support page actually hadn't been updated in more than a year.
Obviously, Apple meant to communicate something like the company recommends customers install one of the widely used antivirus applications available.
I certainly don't think antivirus software is a must-have on a Mac (as long as it's not attached to a LAN, because you never know what others on a LAN are doing), and you apply some common sense to where you click and surf, and what you download. That said, I still run it, just to be safe. And, because I believe the more market share Apple manages to carve out for itself, the more likely it will be targeted by malware.
Perhaps Apple will soon post a better-worded Knowledge Base article and clear up the confusion the poor wording caused.