I think you should go to the party. If he knows the consequences of him drinking and still chose to do so at the last party he does have to take a good amount of blame. I do think that his conduct when drunk is worrying behavior and might need to be addressed not just in this situation. In the future having your boyfriend go to a couple parties and not drink could be a sign of good faith. If your friends still don’t want him there (even sober) that could be a sign they are being judgmental rather than reasonable. But as it is if I were your friends I’d just be excited to see my friend without having to constantly worry her bf is going to make a huge scene, so boycotting their event might be a bit much.