They are perfectly happy playing in the current open ecosystem, why should they be forced to change?

I'm maybe being a bit dramatic by saying I'll ban them, but they will certainly be given a lesson on taking a stand, and if necessary making sacrifices, to defend freedoms and not give in to coercion.

It's not at all 'microsoft bad', except in this case, it seems they are.

Precisely, it's a teaching opportunity. My parents denied me certain things, and while I "hated" them for it sometimes, I have grown to understand why. It did have the very real cost of making socializing more difficult, and yet precisely that prepared me for this kind of sacrifice. Long term, I'm grateful for that, they were real, actual parents.