YANBU. I'm quite frankly shocked at the posters who say his behaviour is OK. It's far from OK.
Two of my exes were alcoholics, and I recognise what you're saying only too well.
He is sober when he starts drinking, and - presumably - when you try to explain to him what he's like, so he can't blame his behaviour totally on the drink.
Can you video him when drunk so he can see what he's really like, without the haze of alcohol clouding his memory?
But, no, you're not BU at all to chose not to be around someone who is being an arsehole to you. Refusing to be around when he's drinking is drawing a line, and I think you need to do so.
FWIW DP and were both fairly heavy drinkers pre-DCs. On the very rare occasion these days (twice a year if that?!) we get a chance to have a proper drink, I enjoy his company when drunk. We're both happy / silly drunks and have fun together. This is the key difference. You're not saying you have a problem with being drunk, you have a problem with the way he is when drunk. I remember the sinking feeling when my exes were drunk and I knew what was coming
Being humiliated is not my idea of fun, and you should not put up with it.
YANBU in the slightest and the people who think you are either simply don't understand what it's like or just want a fight IMO!