This is a complete red herring and a very sly one at that.
Sure, MS have no obligation to make it so that Safari can run on Windows.
However, Microsoft also cannot stop Apple from building a version of Safari that runs on Windows. Or iTunes on Windows. And when Apple built iTunes on Windows MS had no right to force them to fork over 30% of every song they sold within iTunes to MS. MS had no right to force Mozilla to build Firefox around the IE6 engine, or Chrome around IE6.
It’s very likely Apple, Google, or Mozilla would not have existed if governments (specifically the EU) hadn’t stopped Microsoft from pushing it’s options as the default, never mind blocking alternatives altogether.