In a country/culture they know so little of.
They talk about soveregnty. Yanukovich may have been an asswipe and won an election under dodgy circumstances, but win he did - he was the legal president of the ukraine, essentially ousted by a violent revolution. The whole country wasn't united against him, there have been counter-revolutionary demonstrations in some Ukrainian cities. The new unelected 'official' Ukrainian administration has essentially banned the Russian language in a country where nearly half the population speak it (although the language issue is complicated).
Don't think for a second we're seeing the whole picture. It's an issue of Byzantine complexity. Stop uncritcally believing what you're told. There is a massive propoganda war still raging between the US, Europe and Russia and all we can be sure of is that we're not getting unbiased information from anyone.