Exchange teaches you many things. One is that there are a lot of different types of people in the world. Another (and my opinion, more important) is that not of all of them are good.
There are some people that have convinced themselves that they have already learned everything there is to know about life. Their minds are closed to the possibility that they could learn something new; therefore, any sort of civil discussion with them is not possible. These people allow the stereotypes that infect our planet to spread like they do.
When they come in contact with something as contradictory to themselves as an exchange student, it is easy to see how incompatible they really are.
As an exchange student you are sent out into the world to breakdown walls between cultures and open minds. But when you’re confronted with that one wall that just won’t break, a few things happen. At first, it’s quite confusing to have someone who doesn’t want to hear what you have to say. Then, you start to realize that the stereotype that you had of a friendly, fair world was just that - a horribly wrong stereotype. In the end, you have no choice but to accept it and move on.
Later, thinking back on it, you begin to understand the reason they threw you out into the world - in learning the lesson that you don’t have the power to change everything, you truly open your own mind to the world and become conscious of the fact that you, yourself were one of those people before.