Why not? They were there first.
Putin has done it: He's pounced on a country in very delicate condition after overthrowing a rotten oligarch, created the illusion of a popular mandate, engineered a vote that wasn't a vote, forced roughly 2 million people into his open arms, and nobody could stop him.
In retrospect, the quote from our man in Kiev, in his post just after President Yanukovych was ousted back in February, is especially bitter: "The price for victory was very high."
And now that Putin has made the Russian-speakers in Crimea "safe," let's see what happens to the rest of the population. So far, one Ukrainian serviceman has been killed and another injured when armed men—and a truck bearing a Russian flag—stormed a military base.