I hate my bfs best friend

I don't know if I'm overreacting or not but I literally get the chills when my boyfriend (unborn child's father) mentions his friend and I get really pissed when he refers to him as his best friend. My reasons are not so much personal towards the friend because I really don't know him that well. To be honest, I've met him about 3 times. The reason I stopped caring for him is because of the way he treats/treated my bf. He sometimes just ignores him and my bf will be calling/texting him and he won't respond. This makes my bf very upset and I have to be the one dealing with his emotional side. I also feel that this guy only talks to my bf when he wants or needs something. He had a gf for the last year and one night they got into a fight so he called my bf to come pick him up. The girlfriend ended up coming outside and kicking my bf between his legs and punching him.  A day later the guy gets back with his girlfriend and neither one apologized to my bf. I told him that he should demand an apology from the girlfriend but the friend just said to him "what do you want me to do? You're not going to get an apology".  
I really find this unacceptable. And I just think my boyfriend is such a good friend to him and he doesn't even deserve it. I have more reasons but I couldn't possibly get into them all. Bottom line is - I cringe when I hear him say "my best friend" or even when I hear about them hanging out together. My feelings hurt my boyfriend though because he feels torn between me and his "best friend". But I'm not asking him to choose. Never would I ! I want happiness for my boyfriend. But I don't know if I'm overreacting or even how to handle this and so I guess I'm just venting here and maybe seeking advice. What do you do when you don't like your significant others best friend? Neither one of us are going anywhere! We're having a baby in three months. I love my bf but I fear it will get worse in the future. I really don't like that guy.