Remember the strength of the original claim in dispute and the use of counter-example:
AC: "the only way to do serious computing..."
boltar: "most of ... those ... are not running Windows"
That's an acknowledgment that there are *some* servers running Windows. The details of market share aren't needed to accept the "only" claim is hyperbole, to put it politely.
Anyway, all this is a distraction from the point that free software, open source and proprietary software have their place. My argument is that a more pragmatic approach with less purism might have gotten us further. Additionally, an ability to move with the times might have led to a better and more unified approach to the cloud service provider loophole.