To Laugh At Yourself..
...is what makes this movie so funny.
To accept that a lot of stereotypes do have a grain of truth and not to be threatened by it is a big step AWAY from hateful racism.
The characters in the movie were so funny because they could rise above the stereotypes by poking fun at them. When you can laugh at yourself and not be offended by the possibility that black people and white people are, in general, not identical, is when you can get away from too much political correctness.