That recommendation would only work for now. Mac will have viruses as the number of mac users rises. No matter how hard or complicated the system is, there will be a virus on the WILD eventually.
http://www.computerworld.com/s/article/9072959/Mac_easiest_to_hack_says_10_000_winner
Hacking will lead to viruses...
People have been saying that for a decade. Hasn't come true yet. Also, PWN to OWN generally uses older versions of Apple's Safari (compared to the patched versions of other browsers) and they have physical access. Any machine is vulnerable if you have physical access to it.