I think the answer to your question is very simple... the Russians have had enough of US/NATO encroachment into their neighborhood. Additionally, I think that the Russians have a legitimate concern that this encroachment poses a direct military threat to their nation.
For the same reason that I would oppose a hostile military power putting forces on the mexican or Canadian borders, I agree and support the Russian efforts, up to and including military response, to keep both the Russian border and the "near abroad" free of foreign military forces.
Russia doesn't own their neighborhood. As a libertarian, you should know that.
I agree with the president.
How/why is Georgia 'their neighborhood'? Georgia is a different country from Russia. Whether NATO expands to include Georgia is not Russia's business. It is not 'encroachment' for NATO to expand to include a country that is different from Russia. Russia does not own Georgia. And finally, NATO is a (not even very effective) defensive alliance; Russia does not and would not have anything to fear from NATO including Georgia as long as she didn't attack Georgia. All of these statements are obvious facts.
By sympathizing with the Russian contrary viewpoint you are conceding that Russia views Georgia as her property and that she has paranoid views about NATO 'encroachment'. In other words, you are conceding my point.
Finally, it is either terribly naive or disingenuous of you not to mention the role the pipeline that goes through Georgia may play in Russia's motives here.
Additionally, I think that the Russians have a legitimate concern that this encroachment poses a direct military threat to their nation.
I think that is a paranoid (albeit typically Russian) view. Pray tell, who in NATO wishes to use Georgia to attack Russia? And for what purpose? Russia is a backwater ("Mexico with nukes" as the saying goes).
For the same reason that I would oppose a hostile military power putting forces on the mexican or Canadian borders,
Neither NATO nor the US is a 'hostile military power' to Russia as long as Russia doesn't attack other countries. Why do you/they think it is? This Russian paranoia is the crux of the matter. Either that or Russia (as often seems) believes it is her God-given right to attack neighbors at will, and considers any impediment to this right to be 'hostile'.
For the same reason that I would oppose a hostile military power putting forces on the mexican or Canadian borders, I agree and support the Russian efforts, up to and including military response, to keep both the Russian border and the "near abroad" free of foreign military forces.
In other words you agree with Russia's imperial designs on the region. Clearly you don't have an actual disagreement with the critics of Russia's behavior. You just think it's ok for Russia to be imperial. Glad we cleared that up,