The fact that Macs are statistically less likely to be infected by malware does not mean they are immune. It just means, that most malware-authors are more interested in windows because of the larger number of potential victims.
(Who came up with the idea to spin the fact that Macs are less attractive to black-hats into Macs being more secure anyway?)
This wasn't so much aimed as a direct response to the joke but rather a general comment towards the fact that there are actually people who want to believe that Macs are actually more secure then any other computer. Sorry for being so unclear.
I have a much classier Keyboard Concierge.