What you are saying is not provable. This is because viruses don't have to give off signs you've got it... that is, in fact, the whole point behind virus protection. Tell me what's better.... being under the impression that your OS can't get a virus while having one and not knowing your OS can indeed get a virus, get a virus, find out you've got it, and then get it fixed. I never said you said "Mac is invulnerable". What I will say is the Mac has had viruses, they have been added to the Xprotext plist (which is NOT mentioned in the link you gave, go figure) and the Mac will get more viruses in the future. That's something to anticipate and count on rather than sit back in a false state of comfort.