Is it OK to have sex with mentally retarded persons?

I think this film was meant as a romantic love-story – or maybe a vehicle to show how sexy Mel Gibson is! ;-) – but anyhow as entertainment. Also for me it was first only this. However afterwards I had to think about it the real question that lies hidden under thick layers of sweet romance: is it OK to have sex with mentally retarded persons? And this is not just a theoretical question.

Of course in the film everything is presented in the most ideal way. Although she is Tim’s senior by more than twenty years, Mary is still attractive and she only wants to be good to him. Moreover she sticks to traditional morals. She waits with sex after their marriage, and she only marries after an “expert” had advised her to.

On the other hand Tim’s sister Dawnie is presented as the bad one, who doesn’t her brother's luck. We the audience know that her accusations are wrong and they don’t have had sex – not yet! However what would you do if you were in Dawnie’s position? You have a mentally retarded but very attractive brother - such people do exist! - and some older woman who wasn’t able to find a normal husband seems to be after him.