Don't know why this got downvoted. Communism has killed more than Nazi's, so if we're banning Nazi's because they're a potentially violent threat, it follows that communism/marxist subreddits would also be banned.
Glorification of the USSR would be more complicated, and could be perceived as endorsing violence.
If we're banning one -ism because it's considered violent/hateful, we need to ban all of the -isms that are more hateful/violent.
Communist governments have killed more than Nazi governments. Banning one without the other is hypocritical.
Perhaps Reddit is okay with being hypocritical, just as long as they own up to it.
They do advocate for millions of class enemies to be killed.
Personally I feel, and I know many people disagree, that parallels between today and '30s are overrated.
While history can rhythm, the modern left and right have mythologized that period to the point it is unrecognizable.
People don't actually read books on WWII.
That is, though Marxist Communism talks about everyone being equal, it also talks about violence to those who disagree. And in practice, the violence has shown up more reliably than the equality has.
Only because the USA decided to enter WW2 and helped defeat Germany. If the Nazis had won you would be looking at greatly elevated body count numbers today. After all Hitler viewed Aryans as the master race and all other races inferior, and the extermination of the Jews was simply the beginning of his grand plan.