In vino veritas -- and a certain measure of character

One definition of a decent person is someone who needs to get drunk before telling you off. One strong and consistent correlation seems to be between inhibitions and good character. The reverse holds true too, as demonstrated by sociopaths and their utter lack of inhibition. 

Thus, one of the best measures of character is the gap between a person's personality when drunk and when sober. Decent people generally aren't harshly critical because they would feel bad about hurting others' feelings. "Feeling bad" about such is proof of the existence of a conscience. And needing alcohol to rid oneself of conscience-derived inhibitions is what people with strong consciences do.

They say there's no such thing as a mean drunk, only a mean person. Maybe so. And whenever someone says, after the fact, that was just the alcohol talking, that's pretty lame: obviously, it was the person talking. But anyone who needs alcohol to allow his inner critic -- or inner hedonist -- to come out is actually demonstrating a certain measure of decency.

The people you have to guard against are the ones who are uninhibitedly loud, obnoxious, and mean while stone sober.