People can make sweeping judgements based off of one interaction. Try to catch yourself before this happens in your life.
If you let yourself go with the flow of feeling, it can be easy to make broad statements about people that are unlikely to be even vaguely accurate.
It’s too easy to have one bad interaction with a foreign national and then say all of them are like that. Our mind tries to protect us from all of the similar bad plants, animals, people, etc. The nuance that this is one bad person, or even one bad situation involving that person, is hard to sift out.
If one politician says something you don’t like, you might say something charged about all politicians, without proof, experience or knowledge.
Remember too, this works both ways. When you are arguing for or against something, you are representing a host of people that look, sound, are titled, or are in a club just like you. Those others will get smeared by the same brush used to tarnish you. Try not to give people the opportunity to associate you with negative things.