Edit: I didn't want to litter the thread with copypaste, but my reply to the same question from another user was:

  In 1960s Germany, students where so outraged by the absence of Nazism from their history curriculum that they turned violent. They rioted, bombed, and killed because they felt they where being denied their right to learn their recent history. And they blamed this on the fact that their teachers and parents had been Nazis and thought they where trying to erase their crimes. In a flash of cruel irony, the state's desire to shelter the students from political violence ignited it again in the streets and in the hearts of their students.

That’s fine, but putting up a statue of someone is usually seen as celebrating them. We aren’t hiding from what Hitler or Stalin did, so why don’t we have statues of them?

Perhaps it is the reason why the Reichstag still today has a mailbox with Hitler's name on it.

  Another really cool feature is the this hall of mailboxes which was designed by a french artist and includes a mailbox for every democratically elected official in German history. The hall also contains officials such as Hitler and Goebbels because they were democratically elected but they often have to repair the box because people visiting will often punch and kick their boxes