My boyfriend is mad at me cause I pushed this girl but why?

I don't get it. I mean here's what happened my boyfriend is on the football team here and he was the reason they won, since he scored 2 touchdowns and some girl who is on the dance team came up to him after the game and hugged him and kissed him on the cheek I was so mad that I actually went up to her after she did that and pushed her down right there. She tried to get back up to fight me but she was held back not that I was going to fight her anyway but my boyfriend got mad at ME over it when he was the one letting some other girl put her hands on him! He kept saying I don't have to act like a jealous girlfriend and I didn't have to touch her and blah blah blah. I don't get why he would be mad at me. Did I do something wrong that would make him mad because I really don't get it. It's like he's defending her!