When German historian Rainer Zitelmann reposted a photo of Adolf Hitler to warn against appeasing Russian President Vladimir Putin, he didn’t expect it to trigger a police probe. According to police, the problem was the image itself: Hitler was shown wearing a swastika armband — a banned symbol under Germany’s criminal code, which prohibits the public display of Nazi and other extremist insignia. Zitelmann was informed in February that authorities were examining the case. Zitelmann’s is just