Millions of innocent jews and others were tortured and killed by members of the Nazi party. It was evil, and it should be condemned.
But it happened. It's part of reality, and it's something we should learn from. Denying its existence (or acknowledging it in a way) by censoring it seems counterproductive to me. Let's no stick our heads in the sand. There are lots of "symbols of evil" that the Germans do not ban. People see them and are told they represent evil, and they can be taught a lesson about evil.
And let's not forget that the swastika was an ancient Hindu religious symbol that had very positive connotations. People should be taught its original meaning and how the Nazis desecrated it.
WWII happened in the 1940's. The Germans are good people. As a culture, they have always been inventive and industrious. And, like every other nation on earth, they have a sense of superiority. And a long time ago, some people took that sense of superiority too far. In a very Microsoft-like way, they dealt with their "competitors" by crushing them, rather than trying to a better job. (Note that I don't think Microsoft are nearly as evil as the Nazis. Bill Gates is excessively competitive, but he's also a philanthropist and deserves recognition for it.) The Germans and everyone else in the world have to grow up and get past this fear of the past.
If you're a white American, and your ancestors owned slaves, should you be ashamed of yourself? No. You can be ashamed of your ancestors, and you can be ashamed of all of the cruelty and torture that went along with it. But you yourself know that slavery was wrong. You're not responsible for it. You can get past it without pretending it didn't happen.
But that's just my opinion.