Which will change, if Mac ever gets a respectable market share. Even among those who are not religiously motivated (as many anti-MS hackers appear to be), most hackers are smart enough to put their efforts toward the systems that are best able to propagate their work.
With over 90% of the user market, Windows is by far the most desirable target.
But again, we cannot neglect the religious aspects of this: there are those -- and I suspect there are/will be several on this very thread -- whose antipathy toward Microsoft is rather resembles militant Islam.... ;-)