So?

We, in fact, the whole world, have legitimate interests in Syria, North Korea and Iran, and the Russians do everything they can to make things as hard for us there as possible. So why not return the favor?

Look at the map, geographical realities make it difficult for us, or anyone else, to prevent the Russians from doing as they please in their former satellites. But we can make them pay a diplomatic, propaganda, political and economic price, and we would be remiss in our obligations and devotion to our principles if we did nothing to help the Ukrainians.

In my opinion, the Russians have perfectly valid claims to East Ukraine, especially the Crimea where they have large numbers of resident ethnic Russians loyal to the Kremlin and a massive naval base and other investments--guaranteed by treaties we have signed. Probably the only fair solution to this issue would be a partition of the country to reflect this, but once the tanks start rolling, fairness takes a back seat. So Putin has given us no options and little choice. We should do everything we possibly can, short of war, to make him pay as heavy a price as possible.