Whether they consider themselves Russian is a slippery slope of an argument --and not only because I doubt you have trustworthy sources to back this claim. There are many regions in the world where minorities or even significant local majorities consider themselves separate nations.
If your argument that political power grows from the barrel of the gun is to be followed, then there’s no problem with Ukraine using said power to take over Crimea, should they have that capability. That kind of follows from your own logic.