Try going to berlin waving a nazi flag and saying they should have killed more jews back then to see how that goes
He was 4 years old.
If you read again what I wrote it's already there: free of opinion doesn't mean that all opinions are permitted, because some of them are crimes.
Anyway, if you know Berlin you should also know that there have been a spree of neo-nazi violence lately and the police is not doing much to stop it (I lived in Berlin for a few years)
https://www.dw.com/en/berlin-police-admits-failures-over-far...