As soon as God is gone, the only standard to judge things is how well it suits you. You can dress a made-up morality in fancy philosophy; but it comes down to: "that's what the maker-upper fancies." There is no way to distinguish between your philosophy and Stalin's except in fanciness. But fanciness is a preference of the philosopher. Stalin preferred a more direct philosophy and there is no way to distinguish them.
Except for one thing. Stalin has a lot of guns. So his philosophy wins. And there's no reason to think it shoudn't because they are both made-up philosophies.
Stalin's postulates that his personal power is really, really important. Your's may postulate otherwise. But they are arbitrary and indistinguishable by any standard other than who has more guns and the will to impose.
For Stalin mass murder in his quest for power was logical, however his goals would have never been reached if his followers had also been logical. They didn't carry out Stalin's murderous orders in order to give him power. They believed that mass murder would create a Utopian society. Of course it didn't, as any logical person could have told them, but to this day millions of socialist morons believe that mass murder could pave the way towards Utopia. Are they logical? As I said before, God has nothing to do with their irrationality. They are just stupid.