"Given the general profile of Linux users"

That may be true now, but if Linux were to draw a large number of users away from Windows(and possibly Mac) that general profile would change. One of the reasons that the recent Mac virii ave had success, even with a similar security setup to Linux/BSD/Unix, is that many of the users infected were previously Windows users that switched to the "virus-free" Mac. Rmember when Mac users and ads were spouting the line "there are no viruses for Macs"? People bought into that, got Macs, assumed they were safe and wound up authorizing the malware when hackers started writing it.

Switching to a "more secure" platform had not helped them in the least because the basic behaviours which got them into trouble in the past had not been corrected. And having masses of people switch to Linux would net the same effect. It does not matter how secure a platform is if the user behaviour is not fixed. Once the platform becomes a large enough target hackers will start trying to break it in earnest.