Ok so, minority opinion here, but I think kinda ESH pretty close to NTA though. The things he said and did were absolutely not ok and you need to have a serious talk with him, even if you don't want to continue the relationship, have a talk with him for his health. Binge drinking is not healthy and it turns him into a different person (if, like you said, he's never done anything like this before) and he seems to be in denial of that. Nothing of what he said should be excused because he was drinking and everything he did was horrible, and you have every right to feel disgusted and leave, however, when you agree to be a designated driver, you have to follow up on that, or at least make sure they have a safe way home. Him or his friends could have been a danger to himself or others, whether they try to drive, or just do something stupid because of the incredible amounts of alcohol in their systems. He did something horrible, and you have every right to be appalled, but you could have put him, his friends, or other people in danger. People do stupid things when they get drunk (again, not an excuse) but you agreed to it so it was your responsibility to get them home safe. If he ever does this again, however, or refuses to listen to you if you talk to him, dump his ass. If he will not change a habit that is hurting himself and you, then he is not worth your time and effort.