It's certainly part of his real personality. Bottled-up emotions that don't normally get expressed will tend to come out under the influence of alcohol. A lot of people suppress their sorrow or their anger or their lust, etc....and they'll reveal it much more clearly when they've had a few drinks. This is one reason why people want to drink, it helps them let go of bottled-up emotion.

I think that if your friend was not angry, he wouldn't get that way when he drinks...so the question is, what's he angry about? And are there are clear ways of resolving what causes that anger? He must be angry at women, for one thing.

Liquor seems to make me get merry, relaxed, and cheerful...but I've never tended to overdo it.

The classic stages of heavy drinking are said to be:

1. the "happy" drunk
2. the maudlin drunk
3. the angry drunk (worst stage!)
4. the comatose drunk

I've never gone past the "happy" stage.

By the way, I enjoyed the video with the scientist. I don't really agree with him in the larger sense of what he's saying, but I think what he was saying worked fine within the vert close parameters that he clearly wanted it to remain within. It was "true", but probably not the whole truth.