Thank you!
[spoiler]Lindsay Lohan Fan [/spoiler]

I beiieve that was because while there was little sex or violence in the film, it actually dealt with rather serious family issues that children might not be able to understand or interpret correctly. In suggesting this, I am not necessarily in agreement with your parents.
You don't have to be a psychology major to know that both the man and her mother got issues. The man was obviously a mama's boy who had an unhealthy attachment to his mother, and dared not confront her on any matter - except at the very end. Little need to be said for the mother, who was obviously a psycho case. She had to be in control of everything. In particular, she had to be in complete possession of her son. She was afraid of losing him to "the competition" - meaning his wife. She regarded the wife just as an instrument to generate an heir for the the family - just like breeding horses, you know? After that, she wanted her dead.
This film is highly unlikely to improve people's relations with their mothers and in-laws.