One of the biggest problem with people in general is that we judge each othrer so much and that is really wrong. We more often then not judge a person by the way they look and not what the person is truly like. People need to take a step back and look at themselves before they start judging others because we all have faults.
I think it is bad to judge people to a point. I think that judging somebody on foolish reason is something that doesn't benefit anybody. But judging somebody based on any criminal activity, etc, isn't a bad thing. I think it just depends on how you decide to judge somebody.
It is not bad to judge people from the start. It is however bad to act upon that judgment till you get to know the person better, they may change your mind. It is always good to have a bit of an idea about the person so that you are not going into the relationship unaware. Most people who act or behave a certain way do not change so the judgment that you form will usually be right.
In actuality, it is absolutely necessary to judge people. The world is full of serial killers, muggers, con artists and users. Failure to recognize such people by exercising good judgment is a sure way to wind up, bankrupt, broke, raped, beaten up, and dead. Worse, failure to judge correctly which people are of both good intentions and competent to execute those intentions means lost opportunities and missed good friends.
A judgment of a person can be a very private thing. A person doesn't have to hate or even change their attitude towards a person, but to make a judgment about a person is a very natural and fine thing to do. It allows for safety, friendships, and understanding others.