Communism is a political philosophy which in and of itself does not advocate for oppression. There is indeed nothing wrong with it, at least if you advocate for freedom of thought.

The Stalinist version of authoritarianism has been conflated with communism by american (mostly) media during the cold war. It is however a very specific ideology.

Apologists for authoritarian regimes, whatever their political leaning, deserve no platform or tolerance. Plurality of thought however is needed and essential.