Two things can be true at once. What Russia is doing is barbaric. What Ukraine's government has voted against in the UN, such as anti-Nazi resolutions, is also a terrible thing. You can criticize both. This isn't a game of "pick a side."
Also a lot of leftists have realized that the idea of "perfect victims" is deeply fucked up for Palestinians but when it comes to Ukrainians Russia can massacre village after village with large parts of its military being full of Nazis but God forbid one Ukrainian division has Nazis which is bad