But user, the sociopaths have always been inside the party. It's both common sense and proven fact that structures of power attract sociopaths, so they flock to big political parties. And when there's only one party, well…
Lenin knew that letting any retard join and climb the ranks would be a disaster, so he tried to create a complex, years-long process to groom promising, intelligent kids as revoolutionaries all the way to adulthood in the Party. It makes sense, because he regarded loyalty and discipline to the Party to be absolutely central to the Soviet system. But it has one fatal flaw: when you have just one path for people to participate in the political process, that path will inevitably be clogged with opportunists, arrivists, and other assorted sociopaths. In other words, the very last people you want in the Party.
And this definitely wasn't a problem only later on. I mean, Stalin's inner circle was… less than noble, with its Berias and Yezhovs, and possibly Stalin himself. See what I'm getting at, user? The very persecution and gulags which you regard as problem-solving tools were themselves the products of sociopaths. And from them we get to an old discussion: yes, that totalitarianism kept the system stable and the country running, but at an immense human cost, so was that system worth keeping in the first place? That's a matter to fill entire books, but I'm just bringing it up here to get you to think on it.
As the years went on, and people felt more alienated from the government-party, the proportion of parasites inside the party only grew and grew, till we got the bastards we mentioned. It was a flawed design in the organization, not a lack of authoritarianism and slave labor, for God's sake.
Here's a couple of posts that I made defending the temporary authoritarianism of the revolution:
So I'm not against the concept as the means to an end, but it simply can not be a permanent thing. If it does become permanent, then at the best possible scenario you have killed the revolution to save the revolution a la Napoleon: you sacrificed its bigger goals in order to guarantee other goals. In Stalin's case, I hardly need say he created an anti-humanist system that forsook the majority of the (admitedly lofty) demands of socialism in other to guarantee the safety of the country. You can say he made the best of a shitty situation, but in the end, Stalinism was simply a society not worth keeping.
I understand your willingness to use violence against reactionaries who would harm society for their own good, but the thing is, this isn't something you can objectively measure. If you could somehow detect them with no harm to the people at large, by all means, gulag them all, and you wouldn't even need to build a totalitarian nightmare for it to work. Until such a day arrives. But until then, the human cost of such a system would be far too high.