I think perhaps what this means is that the age-old excuse "I didn't mean it, I was drunk" is a lie. A better saying might be something like "A person shows you who they really are when they are drunk." Alcohol lowers inhibitions, and we do say/do things that we think but would never say/do sober. That doesn't make any of those things true.

Cats4, probably he would think that anyone is selfish because they are not catering to his every whim 24/7 and they will also make decisions based on what is good and healthy for them sometimes. It's probably not personal, he likely sees everyone he's ever been close to as a liar and selfish. I'm betting that he does this with everyone he dates, if it wasn't you it would be the next unsuspecting person who falls for his act.