Desktop Windows gains it's monopoly leverage from running Win 32 apps and people are forced to run it for compatibility. None of those programs will ever run on Windows RT. Windows RT is basiscally starting from zero, just like the iPad did.
Just because it has Windows in it's name does not mean it's subject to antitrust. What next? Insinuating that Windows Phone should be subject to anti-trust restrictions that the iPhone or Android is not?