Boyfriend's brother took a picture of my buttcrack?

It was his birthday party and he had loads of friends over. Anyway I bent down because i'd spilt some of my drink and i didn't realise until I got up that my butt was showing. He wanted to look funny in front of his friends so he took pictures of my crack and sent them to everyone. When my boyfriend found out, he got really mad at them and demanded that he deleted them. He deleted the one on his phone but he still has more of them. How can I get him to delete them? Why is he being such a dick to me?
Boyfriend's brother took a picture of my buttcrack?
Post Opinion