IMO, that sense of security comes less from a confidence in the Mac OS, than it does from a near-religious conviction on the part of Mac users that hackers really only hate Microsoft.
I won't pile all Mac users into that box, but in my experience there are a lot of people for whom "being a Mac user" includes a hefty dose of evangelistic zeal.
As for the hackers, they do include a goodly number of anti-MS types. But hackers are hackers first, and Mac OS is just another target.
Well, I'm a Mac user (as well as Windows when I have to), and I would argue the exact opposite.
Hackers don't hate Microsoft - they LOVE Microsoft.