Edit - Those English people moved to Spain btw. The Russians in Ukraine, for the most part, did not move there.
They had to have moved there or they would be Ukrainian not Russian. I do realise it's a bit more complicated than my somewhat stretching it (to say the least) Brits Abroad thing but the underlying part about at what stage does a population cease to be immigrant and become naturalised is of some relevance I think. I don't know enough about Russian (and surrounding areas) history to really know but I believe there was a lot of enforced movement of peoples around the place during Soviet times so can see how various groups could have issues about where they happened to have ended up. They may have had to have moved there to be there but that's not to say they necessarily chose to be there.
However, I'm not so sure that deciding that because a given population ended up in a foreign (to them) nation for whatever reason means they get to decide they now own or control it - what about the people who lived there originally and presumably still do? I vaguely recall it being a Soviet policy at one stage to mix up populations and move them about from place to place so as to try to homogenise all under the Soviet banner. As I said, I don't know enough about the history to really say but would imagine it's that kinda stuff that's causing many of the problems in former Soviet countries now in various stages of revolt and uprising of one sort or another. I agree that Russia has legitimate reason to be concerned (NATO bases on their borders and the like as you mention) but given it was essentially Russian (then Soviet - Russians were largely in charge of that afaik) manipulations that are perhaps the root cause for these situation (or a goodly part of the cause maybe) I'm not so sure they get to decide the fate of other nations again. Didn't work out so great last time or they wouldn't be having to do it again now. Seems rather like chickens coming home to roost almost.
Having said that, as I said above, the minimal force used so far is at least preferable to what looks like could very easily flip over to considerably more force. That doesn't make it right though.

