Humans are biased. We're designed to identify people who are different from us, people we have things in common with, and people who pose a threat to our safety - emotional & physical.
It's easier for our brain to make a decision about a person when we allow our bias to control it. But how many times have you misjudged someone you met, for better or for worse? When we rely on our bias to make decisions about a person's potential as a friend, foe, or neutral, we seriously limit the potential of the relationship.