If the overwhelming majority of my nation wanted to be the 51st US state, and America wanted oblige, of course I’d be okay with that! For god’s sake man, America literally invades countries under the sole pretext of “spreading democracy”, spreading the right of people to determine how their government behaves. Countless wars have been fought over the right of citizens to self-govern. If the vast majority of Australians wanted to be American (I personally have gone on record saying we might as well because we’re a US vassal state already), only someone who doesn’t believe in democracy would try and stop them.
And it wasn’t just a referendum; multiple NATO polls have confirmed that it was indeed the will of the Crimean people by an overwhelming majority.