A train of thought that I’ve been following for a while:
Kind, humane people are likely to do kind, humane things. But when trying to get their opinions or evaluations, they’re likely to lie or deceive to spare the feelings of others; they’ll avoid being hurtful, even if it means they have to stretch the truth to do it. So the nicer they are, the less the nice things they say can be trusted.
Cruel and hateful people, however, are likely to say cruel and hateful things even if they’re not true. But when they’re true, they’re probably going to savor the infliction of pain. So the mean things they say aren’t trustworthy. Their kind and humane statements are far more believable – begrudging, possibly dragged out under duress, and at the very least are compelled by circumstances.
So the behaviors that are most like the characteristic personality traits of the people we’re concerned about are the ones we should have the least confidence in, all things being equal.