Sounds to me like this guy does not want to be in a relationship anymore. You said yourself he's made the decision for you, not with you. I'm on the move-on-and-find-a-yummy-vegan-boy boat. I know it's easy for someone on the Internet who doesn't know you or your boyfriend to just say something like that, but honestly we've all been through breakups and it's never easy and it's usually for the best.
Another thing that clues me in that this guy is just looking for a reason to break up with you is that different eating habits are not a big deal. It seems like a cop out to me Yeah it's tough to be criticized, especially by your sig other's family, but we deal with criticism on a practically daily basis from the rest of the world and it's no reason to stop leaving the house. So why should a few awkard situations mean the end of a relationship? EVERYONE has trouble at first with an omni family, but it gets better over time. Hell, I'm married to an omnivore, and my family is vegetarian while his is as mainstream as it gets. But that never stopped us, because we always believed in our union. Sounds to me like your boyfriend doesn't really believe in your union.
As far as whether or not you should talk to him about this: yeah, it couldn't hurt. But I'm warning you, if the boy wants to leave, he'll leave.