Completely agree with you. This type of behaviour should attract zero tolerance. I was on a Eurostar train the other night and a group of five foulmouthed 'hooray Henries' who had obviously enjoyed a long and liquid lunch started abusing other passengers and throwing food and beer cans around. The train staff handled it in an exemplary manner and the louts were escorted off the train on arrival by security as a result of a formal complaint made by three passengers including myself.
As far as, in your event, serving further alcohol is concerned, it might seem inappropriate but it may have achieved the desired effect of making him fall asleep, however, it's a high risk strategy.
Yes, I think you should escalate it to the authorities as a formal complaint.