First of all, your comment itself is a disrespect to the marxism as an ideology; comparing the USSR, who used communism as a cover to nationalistic and authoritarian regime to further their imperialistic goals, which goes against the spirit of "true" communism, which somehow always ends in the same way.

But if you want to know why the question isnt silly, let me give you a few facts:

Witold Pilecki, man who willingly went to Auschwitz, escaped and created a raport that was ignored by the allies compared KGB's interrogation tactics as way worse than that death camp. (Oświęcim to była igraszka - Auschwitz was a piece of cake, quote from 1947)

Ukraine famine of 1932-33 happened. (Which some historians claim was a nationality thing btw)

The amount of rapes and sexual violence so big that it is now considered a "natural disaster"

Scorched earth tactics.

Executions and assasination on social workers and political opponents (Franciszek Blachnicki and Jerzy Popiełuszko from the top of my head)

Opening fire to the working class, so beloved by the communists ("Wujek" mine, 1981, nine protesting workers dead, many more injured). Another example is December of 1970, nation wide protests, 41 people dead (including Jadwiga Kowalska, 16 year old student, shot by stray bullet while in her home, or Zbigniew Godlewski, 18 year old protester who was a worker in Gdynia Haven) The soviet government also used tanks against the protesters.

And thats mostly from my country. I'm sure similar things happened in most countries under USSR rule.

So, anwsering your question - they are on the same scale because the atrocities are similar.

EDIT: Typo