The American education system being what it is, I suppose it is possible he hadn't learned much about the Holocaust, but man that statement makes him come off as an ignorant moron. I think most companies, particularly public companies, and especially ones in entertainment, are going to get rid of employees having pictures of them just doing a little Hitler impression in their free time.
I'm sure you can see the difference in a satirical stage show/movie by a Jewish creator who participated in the Battle of the Bulge, and someone from the cast doing the HH with a toothbrush mustache at home, even if as a joke.