I think he sees a side of her that no one else can...the side where she is only trying to protect the only family she has left and how she will always be scard from what Royce did to her. Yes, she can be mean but she always has good intentions.
Protecting your family doesn't make あなた a pighead. Emmett sees Rosalie as his Angel, the woman who has saved him. He sees the beauty inside and outside of her. Such a waste that people thinks she's a cold hearted b*tch. That's why she's my お気に入り character, she stands up for herself and she knows what she want. She's a strong, caring and beautiful woman. That's why Emmett's loves her. But that's just my theory.
i think he loves rosalie because she is strong in her own way and won't let anyone hurt her like royce did. and when she is being mean normally there is a hidden meaning like when she was mean to bella because she was jealous of her being human and of edward wanting bella and not her.
