An additional aspect here is that the Jewish musuem asked to borrow a painting for their exhibition of 'booty art' - artwork which used to belong to Jewish citizens before they were dispossessed by the Nazis.
In one sweep, Prince Hans Adam not only refused the loan, but managed to open himself to criticism to trivialize the Nazi 'Third Reich' by comparing it to current Germany, he achieved that everyone may now wonder how he came into possession of former Nazi 'booty art' in the first place, and he made himself appear upset at Germany because of the ongoing investigation into his dubious financial dealings... all at once, in one official letter.
It's reported all over the serious press, and IMO it was a most ill-advised and incomprehensibly stupid move.