First of all, being impolite or rude to another person is sometimes helpful for people. We may take children for example, do you still remember when you were a child who was not mature enough to recognize mistakes by yourself. Though you have been told for many times never do that thing again, you just neglected all those warning and insisted making mistakes. What would your parents do? Of course, most parents will take some actions which may be more or less rude while very useful, like spanking and scolding. When little childern were frightened by their parents' behavior, they would have no courage to make the same mistakes again next time. In another word, some impolite behavior is a necessary part for children to form good habits and get rid of bad behaviors. There are lots of similar situations during our life time, like when we berated by teachers or loudly shouted by boss.
Second, to be impolite or rude could help people keep healthy and maintain a balanced mind. Nowadays, many people repress their pressure and upset until feel exhuasted. Most people are told to be polite and courteous in public, so that they have no chance to express their true feeling and emotion. Especially for some officers, they need to set a well-mannered example for other employees in the company, at the same time, plenty of pressure surround them as if with a flood. It is not rare that many middle-aged officers suffer from depression because of repressing upset emotions. So, to be impolite occasionally when feeling depressed is a way good way to relax oneself and feel happy.
Third, when other individuals are