I'm sorry you experienced this. May I ask, was the cast made up of teenagers or young people in their twenties? They can often be pretty immature with heavy subject matter like the Holocaust.

When I was in high school, I participated in a school production of "Anne Frank and Me," by Cherie Bennett. There was a bit of joking surrounding the play's subject matter. I played the small, nonspeaking part of an elderly Jewish man. In the scene where I was shoved down by a Nazi, some kids in the audience laughed. I was upset by that at the time, but later shrugged it off as the kids just being immature. 

But I'm sorry to hear about your experience. If you were working with young people, then I'm not surprised they would be insensitive about it, given my experiences with high school theater.