I have a different theory. We actually know in most of the time that what are the issues which can give us hard feeling. And what happens is that whenever we get amazed by a person or a situation or simply we get used to a situation, if it has that trait which can make you feel bad, we start to procrastinate to accept the fact. We try to make ourselves overlook those till the point which is just unbearable to us. But the fact of the matter is that people usually do not change drastically to fit into your criterion because they have their own life. And in a situation when you yourself is trying to denying the potential of someone/something to make you feel bad, that will also deny it till it does by any of its inherent quality which is so natural to it.
We always try to explain events in the light of our understandings. And when we cannot do it, we stop thinking about it unless you practice to do otherwise consciously. That is the reason behind not accepting certain things believing things will turn out in our way. Our mind always try to analyse a situation with the resources available to it and if you restrain an information by not accepting it, there is a possibility that our mind will not be able to break down the situation which is the outcome of that very information to a level in which your consciousness can understand.
I have seen that if you accept that certain person act in certain way, certain groups of people will always think in a certain way, it is all really very easy to explain everything in you own mind. Reality is after all, how you perceive it. There is a point however to note that by accepting people does not mean to assign a value to it and belittle them, rather respecting their individuality as an independent human being as well as in a certain group. By accepting and respecting a person you give that person a room to be what he or she really is and you give yourself a room to live freely.