It makes the character Adam look weak and someone who can be ridiculed and belittled by other people. The father-in-law is so unlikable in the movie too. I'm autistic, so maybe that's why this movie gets me angry. I've had to deal with people like that on occasion. It makes me sick.
Many movies have become popular because many people deemed them offensive. Movies like Dogma wouldn't be where they are today if bodies like the Catholic church banned them from being seem. Being controversial is often the best press a movie can have. When people say don't go see it, others are more apt to see it because that's how human nature works.