That’s the problem with Leninism.
The (biggest; there are others but this prevents even useful discussion of those) problem with Marxism is that people (even those who oppose Leninism and disbelieve everything else associated with it) accept Leninism’s propaganda that it is Marxism, rather than a system which adopts the rhetoric and stated end goals of Marxism, but abandons both it's mechanisms and explicit preconditions.
You are, of course, free to say that the murderous regimes that have popped up again and again are not the true Marxism. But then you have to explain why the false Marxism has appeared so often, and then to explain, given that millions of lives could be at stake, how to prevent a recurrence.
That's only a small piece of vanguardism, which while it is a big change isn't the only significant change (and is, in fact, an adaptation to the fundamental change, which is abandoning the prerequisite of the development of a broad working class identity under developed capitalism.)
> You are, of course, free to say that the murderous regimes that have popped up again and again are not the true Marxism.
Well, I mean its self-evident true, and I didn't need your permission, but thanks.
> But then you have to explain why the false Marxism has appeared so often
I don't see why I should, since I am not advocating Marxism and, even if I was, the reason a system designed to be workable and leverage existing dissatisfaction in undeveloped, precapitalist conditions keeps doing so is neither nonobvious nor germane to discussing the merits of a different system in the developed world. Leninism has done horrible things in the environments which it was carefully crafted to thrive in, but even with the assist given by it's opponents fear mongering equivalence-drawing that painted all opposition to capitalism as equivalent to Leninism, it's done stunningly poorly at gaining any traction in places that don't have he conditions for which it was adapted from Marxism.
You're comparing apples to oranges here. The crimes you mention are all about subjugation of or violence against foreigners. Ill will towards foreigners is the human ur-prejudice -- it's older than our species, in fact. Giving in to this prejudice is something that could have happened under any politico-economic system. It happened under capitalism because capitalism is what we had then. If the world becomes a Marxist utopia tomorrow, and we travel to the stars, and find technologically underdeveloped aliens, it will happen then under Marxism too. It was certainly the case that the Soviet citizenry, however far advanced along the road to true communism they actually were, were perfectly happy to join the Red Army and oppress the hell out of the people of Eastern Europe for fifty years. And they did it they were told they were protecting the world from imperialism from the West!
The problem with Marxism that I'm talking about is much more specific. Communist leaders have a habit of liquidating populations that they deem insufficiently loyal. That's why Stalin killed the kulaks, Mao killed the educated middle class, and Pol Pot ordered the killing fields. Under capitalism there is no comparable tradition of massacring political enemies. And since political enemies are going to be a fact of life under any political system, thoughtful Marxists should worry a lot about how to protect them from the attentions of the state.
Are you saying there has never been a dictatorship or authoritarian government with a capitalist economy?
Capitalism and socialism are economic systems, not necessarily ways of organizing a government. You can have capitalism with or without democracy. Democracy is the true tool against authoritarianism, not capitalism. And I don't think the people in this thread that are arguing on behalf of marxism want to do away with democracy.
Again, to play this game, we could just as easily say that your crimes are all about authoritarian dominance hierarchies, which certainly occur under capitalism, as well (how many people did Pinochet throw out of helicopters?)
People try to rehabilitate Marxism every so often, but the problem of the murderous regime pops up again and again, for a simple reason: when the state arrogates to itself enough power to remake society according to some Marxian vision, it opens the door for abuses far worse than anything Amazon will ever perpetrate.
Are you sure you're not thinking about Social Democracy instead?