As tacky as I think his comment was, I don't think it's insensitive.
He's a musician who appeals to teenagers and Anne Frank was a teenage girl.
Judging by the first part of his comment he found her inspiring, and expressed
his hope that she would've found him inspiriting/entertaining as well.
People need to not be so hyper-sensitive.
Well there goes his chance of becoming President. However, he becomes a strong
contender for VP.