Communists first targeted classes of people. First it was the former nobility and their service staff, then military officers, business owners, land owners. When they ran out of those people to kill, they started inventing new classes to target, like those that didn't agree with the party line, backers of one of the high ranking party members that fell out of favor, religious minorities, people who were taken prisoner during the war, and so on.
As for racism, there's was plenty of that too, only their slogans spoke otherwise.