You can scrap the 'security through obscurity' because that's something quite different.
Nobody said that OS X was safe, it's just that momentarily it's safer than Windows [insert version].
If your definition of "safety" is "likelihood of attack", I suppose that's accurate. What we're saying is that the "likelihood of attack" is directly related to the population size using that particular platform because of the quoted "security through obscurity" -- and that can change at any time so it shouldn't be considered reliable.

So I guess we're in accord: Macs are less likely to be attacked AT THE MOMENT, but that statement should be taken with a grain of salt since we cannot predict the future popularity of various OS'es.

I mean, by the very statement "Switch to Macs, Macs are (at the moment) safer" you're undermining your (well, not yours since you don't use it) own security by attempting to gather a large population base. Technically, it's in your best interests of security to prevent people from adopting the Mac OS. Amirite? hehe