The Russians can be evil without having 'started' this particular incident. The two are not mutually exclusive. Besides, 'who started it' is a children's game; in the reality of geopolitics you can trace these things back forever and get nowhere (see also: Israelis/Arabs). Russia had troops in these regions, weaponry and tanks and invasion plans at the ready, but the Georgians 'started it'. Ok.
Who 'started it' is less important than what the respective sides are actually doing and what ends they seek. What ends does Russia seek here, by your estimation?
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.