I'm not going to talk up Russia or their actions here. It's not a system I would want to live with, nor do I particularly like Putin at all. But he is a very strong politician, much in the mold of our greatest presidents.
As to the Ukraine issue, it's a tricky question and I'm not familiar enough with what locals think as to ownership and country. Heck, wasn't too long ago the US went down to Panama and ousted the government there because we had "interests".
Killing one person is murder, killing 100,000 is foreign policy
The issue is that the Ukraine government gave up their nuclear weapons in exchange for a vow that we would protect the integrity of their borders. It turns out that was a chump move in which Russia, the USA and Britain tricked the Ukraine government into vulnerability to invasion and conquest - which has now happened.
There is no possible disarmament or non-nuclear proliferation agreement to be reached with any country in the future as it has been proven it is just a trick to try to convince the leader and country to voluntarily expose themselves to invasion. Why would any country make an agreement to not develop and keep nuclear weapons knowing such an agreement is worthless?
That is the issue, not the Crimea. Care to argue with that?