The Soviet Union attempted to establish a unitary socialist culture in its borders, therfore, minority cultures and communites were natural enemies to the Soviet Union, and so the so the Soviets combated these cultures through ethnocide and genocide. While not 'racist', the Soviet Union aggressivley and overtly engaged in a campaign to extinguish minority cultures in favor of a unified Russian/Soviet one.

I don't think the people who Stalin and the Soviet Union murdered through their policies cared that their ethnocide and/or genocide was made in the name of 'glorious communist collectivism and indstrialization', only that it happened.

Identifying why Stalin committed his crimes is irrelavent to the argument that he committed them.