Robert Graves said that a true Englishman is prepared to make a joke about anything - even his own death.
But for something to qualify as a piss-take there has to be a reasonable chance that the piss-takee will see the funny side.
Jews very rarely find jokes about Nazis funny. Unless you're Mel Brooks.
And Bosnich - being of Croatian descent - was on slightly dodgy ground to start with. In WWII Croatia was well behind Hitler, for its own grubby nationalist reasons.
A Croatian ex-girlfriend of mine once got a call from her mother, telling her to go out and buy the paper - on page 3 there was a photograph of her grandfather, `when he was young, looking very handsome.'
She went out and got the paper and found the picture. It was from 1941. Grandad was in SS uniform and receiving a medal from Hitler...