Judging is natural and not a bad thing.
The problem is when we judge each other based on trivial differences and paint the whole person with that judgement. It's ok to not like something about what another person does. Just realize that one characteristic doesn't mean the person is totally bad.
Unfortunately, we do have a tendency to stereotype. There's a lot to think about in this world, and we tend to create shortcuts to thinking about them. This includes dividing up who we like and dislike. Generalizing is not always bad, but it should be recognized as such and not depended on too much.
We can reduce these tendencies to stereotype others by thinking of the world as one humanity. Traveling to other countries and meeting more people helps with this. Having friends from other countries in chat groups is a cheaper way to do this. You can also meet people who have moved here from other countries.
However, politics and religion really work against accepting others for who they are. Politics likes to divide people into neat little voting blocks, often using religion to do this. They create wedge issues that define lines and pit people against other people. Religion is worse, though. It paints the "us verses them" mentality as a fight between good and evil with eternal consequences. Even religions that claim to be tolerant only do so to the point that they think they can convert someone. After that, "love thy enemies" turns into "an eye for an eye", "don't be unequally yokes" or "don't throw pearls before swine".
Christians to like to claim that they "judge the sin, not the person", but they don't seem to do this on a practical level. They still tend to do things like trying to take away rights from homosexuals. It would be nice if they could just judge people based on specific actions and not stereotype, but this is difficult when you believe a person is either "saved" or "unsaved".