If there is nothing legally stopping them from doing that, then how is Microsoft going to arbitrarily enforce these new rules?
But Microsoft's store is a private marketplace (despite costing nothing in dollars to use/view). They can make whatever rules they want for the software they distribute or allow to be distributed there. First amendment, etc. doesn't apply. If Microsoft decided only software with unicorns and bunny rabbits could be distributed on their store, they are pefectly within their rights to mandate and enforce it.
I don't care if microsoft's store is a private marketplace. People should have the right to run whatever programs they want on their own hardware.
"Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission."
IANAL, just asking the question, I might be super wrong.