You and I must be reading different constitutions. I see nothing in the First Amendment about videos, music, games, DRM or anything of the sort.
The First Amendment reads:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
From what I read on that Apple post, it sounds like Apple is encouraging you to install multiple AV software. And OS X already runs ClamAV doesn't it? Although I have yet to see such a thing get pushed out, I assume Clam can get updates via SoftwareUpdate?
I don't think they're suggesting that each machine run multiple AV systems, just that there are multiple AV systems in use among all machines, thus decreasing the chances that a virus can exploit a weakness in a particular scanner and remain undetected.
Also, OS X Server comes with ClamAV, but standard OS X does not. However, ClamXAV is available (completely free of course) for OS X and provides a simple way to install ClamAV and a GUI for management. I'm a bit surprised Apple doesn't list it on the recommendation page.
Save the whales. Collect the whole set.