There’s a Chinese communist from the early days of the CPC - and I feel bad that I’ve forgotten his name - who I have read some of his thoughts on this. He said the first generation after the revolution will still have brains full of worms, even among the best and most upstanding comrades. This will get better over time, but you’re talking many generations. Because we are all products of our environment. We cannot escape the social conditions we grew up in. Being a communist doesn’t mean you are now some new person completely cleaved from any connection to the world around us and our personal histories. The Soviet Union did make attempts to fight sexism, racism, nationalism et al within their borders, but thinking you can just propagandize people into right thinking is idealism. The USSR had to start with the social conditions they inherited - and that society, which was part feudalist part capitalist - had a lot of sexism, racism, nationalism, etc (and of course cruelty to animals).

I’ll make a confession: I still sometimes have reactionary thoughts and ideals pop into my head. And it takes active, conscious thought to tell myself “what the fuck dude, cut that shit out”. If I was not actively engaged in checking myself on that, it is possible that the brainworms could come back. It’s something we are all susceptible to in some form, I think.