Memes

Marxists have been discussing the class nature of authority since Marx and Engels themselves, see Marx's Conspectus of Bakunin's Statism and Anarchy and Engels' On Authority. On the whole, soviet prisons and the justice system itself were more progressive than their peers, Mary Stevenson Callcott documented it quite well in Russian Justice. The term "gulag" came from the GULAG administration, and doesn't mean "torture/execution camp" or anything of the sort.

Defending the USSR from undue slander is the only correct path for a socialist to take. We defend the USSR because we defend the achievements of real, existing socialism, and we want to criticize the USSR's shortcomings from an accurate point of view. Any comparisons equating communists to Nazis contributes to Double Genocide Theory, a form of Holocaust trivialization. I'll leave you with a quote:

To place Russian communism on the same moral level with Nazi fascism, because both are totalitarian, is, at best, superficial, in the worse case it is fascism. He who insists on this equality may be a democrat; in truth and in his heart, he is already a fascist, and will surely fight fascism with insincerity and appearance, but with complete hatred only communism.

• Thomas Mann

If you consider yourself a socialist, you owe it to our predecessors to wipe away the sludge cast onto their graves, and carry the mission for socialism forward.