It is simply naïve and ignorant to say the entire Ukrainian population is against Russia. While ~17% of the population are ethic Russian, with more situated towards the east, the population of many major cities tends to be ~50%+ ethnic Russian.
Kyiv, a city with a population of ~3M, is ~54% ethnic Russian and while many will not support Putin - after all he is putting them all in danger and disrupting their steady way of life, some will ultimately prefer to be more in Russians orbit than Europe and the U.S.