This is mostly a serious question. Also, not for the tankies/MLs. I already know what your answer to that question is. I may not always agree with you on everything, but you do have an answer that if the conditions became right, could actually work.
No, this is for the type of anarchist completely against the wall, gulags, seemingly any amount of getting hands dirty. What is the solution to those types of people? There are so many of them in the US, a lot of which are heavily armed, that they could easily topple a socialist system, and even if they didn't do that, their existence would be incompatible with any marginalized group living their lives, since they love to harass them at best, outright murder them at worse. So what's the solution? Anarchists often seem to avoid this, seemingly believing that if there was a socialist or communist society, they would just say "aw shucks, guess I was wrong about that. Guess I'll no longer be racist or xenophobic!"
So am I missing something, what's the answer?
Those were the cases of nation-states in the process of escaping colonialism.
You do have a point, but I'd argue that there was a cost-benefit analysis to slaughtering millions of people in Korea and Vietnam.
In a core imperialist nation, the computation would be different, because instead of killing people in some far-off land (potential trading partner), a government or faction would be killing their own countrymen, harming their own economy and society.