Russia set up the entire conflict. Georgia rose to the provocation, but the whole thing was an act used by Russia to accomplish a preconceived objective. And regardless of whether Georgia was right or wrong in bombing South Ossetia, Russia had no legal right to intervene. It certainly didn't have a legal right to conquer a larger chunk of Abkhazia. Doing nothing in 2008 emboldened Russia today. Russia knows that it has to pay a higher cost for Ukraine than for Georgia, but considering that the latter was virtually 0, why not take the gamble?
The problem with getting a friendly government in Ukraine is that there's no guarantee that government remains friendly (see Kuchma) or that the friendly government wouldn't get replaced by an unfriendly one (twice now). I should note that Russia hasn't tried anything as provocative against Estonia and Latvia since the two joined NATO.
Using all the tools at our disposal might or might not get Russia to back off in this case, but it will send a clear message in future cases. And just what kind of a message are we sending to countries whose security we are guaranteeing and countries that are considering getting nuclear weapons when we so blatantly disregard the Budapest Memorandum? We should stop worrying so much about offending baby Putin's feelings and send a clear message to both Russia and the rest of the world that this kind of behavior is a clear violation of international norms and we're willing to take punitive steps against anyone who engages in this kind of behavior. All I hear right now is a whole bunch of semi-condemnations with no teeth attached. Given Putin's pattern of previous behavior, he might very well take that as a sign that we'd do nothing if he tries to grab the rest of eastern Ukraine.
If Russia is so willing to piss us off, I fail to see why we don't reciprocate. We should take Russia's ongoing aggression in Moldova and Georgia to every international body that's willing to listen. We should do the same against Russia's Armenian ally. Make them squirm. I don't care if no international body actually has the power to rule against Russia; we can embarrass Russia and we can do so over a prolonged period of time.