Is it normal to hate it when people dont respect a relationship?

Basically, I want some outside opinions on this. I'm 19 and my boyfriend is 25 and we have been together for a year and living together for 11 months. We are inseperable and spend all of our free time together as he works a full time job and often weekends too. We live in the same area as his friends, and in the beginning we used to visit them a few times a week. Obviously, because we are in a relationship, we want to spend time together alone and not just with his friends. This was a choice we made together, not something I suggested and he agreed to. I'm not posessive or controlling in any way. In any case, as we cut the visits down to about twice a week as apose to 3 to 4 times a week, some of his friends got really bitter about it. I would hear that they wanted to "talk" with us about why we left the one birthday early, because he had to work the next day. One friend in particular always tried to make me feel bad and like since I came around, they don't see their friend (my boyfriend) anymore, which I thought was really unfair. Basically one of our conversations with the friend ended up with him telling me to go fuck myself, and my boyfriend telling him off for being so rude to me. So end of that friendship. Also, most of the other friends of his stopped speaking to us and got extremely rude with me for no reason as I've always been nice to them. Is it really possible for a bunch of guys in their twenties to be SO bitter with one of their friends for finding someone he wants to spend most of his time with? Also, none of them have girlfriends. So now, they are our former friends due to how they treated us. They also said some pretty hurtful shit about my boyfriend like they don't care about coming around because they have better friends. Seriously? What's everyones opinion on this? Is it normal for guys to be so posessive over one of their friends? If you're going to tell me that friends need to be equal to a partner don't even comment. Friends don't share your bed or give you children so, a partner is supposed to come first. I just want opinions on if those guys are normal or not? Also, this isn't a crisis I'm currently in. This was many months ago but I keep wondering how guys who are supposed to be adults can act so childish.