So Holocaust denial should be banned because it's harmful?

That's the law in Germany.

Which is a bad law, it simply opens the door for banning other "harmful" speech that somebody gets to decide for everybody else. It's the old shameful joke that no one reads history so they keep repeating it.

The legacy of Nazi Germany is a national shame. Millions of people cannot be un-murdered. It could have also resulted in much worse conditions for Germans and national sovereignty (like America's domination of Japan's postwar constitution).

Banning holocaust denial is the national equivalent of recoiling one's hand after touching a hot stove. Most Germans really, really do not want to go back there.

I'm not saying they need or will go back there. I'm saying that the act of banning one type of speech always leads to a group with power and not so honorable intentions the ability to ban speech they don't like. The law is already there for that.