Leaving machtpolitik out of it, there's technically nothing wrong with realpolitik, so long as it's taken with the long view in mind. The Marshall Plan again serves as a good example: A very practical response that seemed altruistic at the time, but offered significant advantages further down the road.
Realpolitik policy based around short-term gains is typically a disaster waiting to happen, since it simply opens the door for future difficulties. Russia's approach to the Georgian invasion is in part one such disaster. Had they limited their actions purely tto the Georgian troops in South Ossetia, the response would likely have been less negative. Despite their rhetoric on the world stage, Russia seems even more entrenched in the "Cold War" mentality than it accuses the West of being.
Pragmatism can provide a semblance of morality in the long term. One of the difficulties with short-sighted policies is that they forget that while the entity you are exploiting currently may be weak, that will not necessarily be the case forever, particularly if you fail to maintain a unified policy over time, something nearly impossible in a democracy.
Which, incidentally, is a selling point for democracy, but that's largely off topic.
Russia manipulated the existing situation in South Ossetia to its advantage. I think we can all agree on that. Georgia dropped the ball in handling the issue, but the question remains as to alternate approaches. Don't forget that the external "peacekeeping force" in South Ossetia was Russian, and that must have been extremely frustrating to the Georgian government.
I'm gonna have to continue this later, kind of scatterbrained right now and I'm finding it hard to phrase things properly. I blame Reya.