The thing is those people weren't even close to Nazis. They just politely disagreed with the hivemind on finer points. All you had to do to fight them was to disagree and explain your position. You already had the crowd cheering for your side, so why should the mods give you even more of an advantage?

The risk of creating a hive mind seemed greater than the risk of being overrun by Nazis, since they got downvoted to oblivion anyway.