This is a true story. (From a Usenet newsgroup):

A friend of mine of German origin was invited to a good friends wedding, his friend was Jewish.

Bernd was at the reception and the room being full of Jews was a little "tense" at a German in their midst.

Eventually of course the conversation turned to the millions of Jews who died in the concentration camps and it got a little more tense and just a little unfriendly as the conversation continued.

Bernd suddenly turned and said in quite a loud voice "I just want you all to know that my father also died in a consentration camp"!

A silence fell, one man said "really? thats so awfull", others joined in their sympathies. What happened to him they asked.

Bernd said "He got drunk and fell out of the watchtower"

The room broke out into roars of laughter and they all had a great time from then on.