Why can't I like him?

Okay so there’s this guy I really dont like, like deep down I can say I hate him. Our personalities dont match at all and we have gotten into it a few times before. Time has passed and I’ve tried to forgive and forget, but I just can’t seem to get along with him. And I know that if I dont like him I should just try to avoid him but he’s like my boyfriends best friend. They spend more time together than we do they have more in common than we do and I guess some of it is jealousy. My boyfriend knows how I feel about him but he thinks its me being close minded and holding a grude ok so if I am. I mean just knowing they are going to hang out pisses me off makes me want to cry. my personality just wont mash with his he carries himself as if he’s better than me better than half the world. He talks down to everyone including my boyfriend. im afraid he’s going to get to the point where he feels comfortable enough to talk about me to my boyfriend and he (my boyfriend) wont defend me. it’s building a gap between me and my boyfriend and I love him more than I’ve ever loved anyone and I feel his friend is going to cause us to split