You're getting a very distorted picture of the facts.
Something else to keep in mind, is the area under dispute. The Autonomous Republic of Crimea. See, it's not exactly "Ukrainian" at all. It is an autonomous republic. The demographics? 50% Russian, 25% Ukrainian, and the balance are mostly Tatars. How and when did Crimea become "Ukrainian" anyway? Oh - that was an administrative move, made by the old Soviet, which stuck Crimea in with the Ukraine. Administrative. Crimea never has been "Ukrainian". So, if an AUTONOMOUS Republic wishes to remove itself from association with a nation that only has administrative ties to it - why not?
There are lots of ethnically diverse countries, and you're making a lot of unwarranted assumptions about the population. A good portion of the Russians (who are actually 58%) may wish to join Russia, but the Ukrainians and Tatars certainly do not.
I stand with Crimea and Russia on this issue. The current regime in the Ukraine are a bunch of racist assholes. Among their first actions upon assuming power, was to outlaw the Russian language in any formal or official documents. Crimeans speak Russian, not Ukrainian. Screw the president, and screw the capital - Crimeans decided that they don't want to be "Ukrainian" any longer.
Ukraine is in the same boat as Quebec in this regard, their native language is being swapped by the major language around them so they take measures to protect it.
Ukrainian was the official language but population re-distribution made Russian speakers dominant in the east and south. In August 2012 Yakukovych signed a law making Russian an officially acceptable language in regions with a large Russian speaking population. This was understandable but also controversial because it means that Russian speaking Ukrainians in those regions lose a reason to learn Ukrainian, thus the Ukrainian language becomes more marginalized and the two halves of the country become less unified.
Either way it was this less than 2 year old law that the parliament voted to repeal, a proposal that the new president vetoed.
There are certainly some parties in the new coalition that are extremist but that's pretty common across Europe. There's no reason to think they'll have strong influence over the government.
Not very many nations are willing to assist another nation in the suppression of an AUTONOMOUS REPUBLIC.
So Russian troops take over the territory, install a president from a party with 4% of the vote, and announce a referendum on joining Russian to happen on March 30th... or rather March 16th. Russian suppression of an autonomous republic is exactly what's happening right now. And don't think for a minute Russia is going to occupy the Crimea, install a puppet government, announce a snap referendum on joining Russia, and then allow a result that keeps Crimea in Ukraine.
I'd actually be surprised if a free an open vote in Crimea resulted in them joining Russia, but I'll be absolutely shocked if that's not how the referendum goes.