The great Simon and Garfunkel music falls flat against a story that neither relates to the music, nor contrasts it. It doesn’t make a bit of sense. The music doesn’t match the mood at all.
It makes for a good thirty second break room joke, having sex with your girlfriend’s mother. This movie is longer than thrity seconds, and it shows. Nothing else is added on of any value.
Instead of being happy about sex, we’re supposed to believe a man is angry because he has sex. You’re right. This doesn’t make any sense. I’ve had sex with sisters, and I was happy. I’m sure it would be the same with a mother. Big deal! This character is terribly written.
Add to this that we are expected to care about this idiot? Why? And why should we pull for him instead of the other guy, of whom all we know is that he is marrying the daughter, and they seem to hit it off? No sane person would care about the Hoffman character getting the daughter. In fact, it would be better all around for him to move on and find someone else. If he stays with the daughter, they all may as well be Jerry Springer trash.
In fact, none of the characters make a bit of sense. It is one of the worst scripts in History.