Its called reading people. I can generally tell what people are like 5 minutes of talking to them by the way they talk, act, dress, and respond and I can generally tell if I will like that person based on that alone. Its not 100% accurate but its close enough to be worth it. Certain behaviors or subjects they bring up will automatically make me think less of them and not want to associate with them. If you can't or don't do this your are either lying, unaware, or not human. I don't call them out and tell them they are idiots I just avoid them.