Hasn't she been through enough?
Look, we can't expect anything better from him. Of course Justin Bieber, still upset over having left his pet monkey at an airport, would write in the Anne Frank House guestbook that he hopes "she would have been a belieber," aka, a fan of his. You can't ask someone who's been a global superstar since he was a tween to not make it all about him. Since before he could grow pimples his job has been to get on stage and accept the hysterical adoration of thousands of teen girls. So naturally, he mistakenly assumes the happiest a teen girl can be is when she's listening to his music/shrieking at his abs in concert.
Also, Justin knows the state of the music industry right now, and he knows the importance of courting every single potential fan, living or dead. Anne Frank being a Belieber means Anne Frank paying money to get his album-only tracks instead of pirating his record, and that's another unit sold on Soundscan. He's just trying to up his sales, you guys. Don't blame Justin. Blame illegal downloading, and the inability of the backwards-thinking record industry to properly market to tragically deceased teens.