Um, shouldn't the country in question decide which sphere of influence they want to be in? Instead of other countries deciding for them?
If, hypothetically, Russia should consider Finland to be in their sphere of influence (after all, Finland was once a part of the Russian empire before it won its independence), should we just stand by if Russia wants to dominate Finland against their will?
We're not forcing Ukraine away from Russia (if anything, Russia's belligerence is forcing Ukraine into our arms). Despite what the Russian propaganda may claim, the Ukrainian protestors who overthrew Yanukovych are not secret American agents. We're not forcing Ukraine to enter our sphere of influence. They don't want to be a Russian puppet. They asked for Western aid. Shouldn't their wishes count for something?
(On that note, I think Crimea belongs with Russia, and I'm fine with Russia taking Crimea, because that's what the Crimeans want. My beef with the Crimean takeover is the bullyish way in which Russia did it--sending in troops, shutting down opposition media, running propaganda campaigns claiming that Ukrainians are Nazis, etc.)