Here's my opinion on this issue:
If Jimmy Fallon wants to move to Fox then that's his right. Yes he's originally from NBC but if he feels like Fox is a better fit in his heart then who are we to say that he can't make the necessary programming and production changes to switch to a different channel? Are traditional guys like Leno and Conan afraid that they can't compete with Fallon on Fox, and that it somehow puts them at an unfair disadvantage? That's ridiculous!