I was shocked at my friend's proposal.what should i do now?

I am a boy and i'm 19.my friend is 17.he is innocent and very sensitive.he has no other friends except me.others make fun of him so he every time trusts me and spend with me.yesterday he proposed me to have .i was shocked at this.i said that it is a gay thing.but he told me that he was d by his cousin(also a boy)when he was 8 years old.he cant understand what is going on.when he realised that he was d he lost his feelings on the women.he behaves like a girl.when we enjoy with movies he used to watch gay .he hate women and loves with men.he told that he lost his feelings on women when he was d by a boy.will it happen like that?he warned me that he will commite sucide if i not accept him.if i tell to his parents they feel nervous because he is only son for them.is there any medial treatment to change him to normal man.i am in a great confusion.i dont want to lose my friend and dont want to sleep with him.please tell me what to do.i am poor in english.if there are any mistakes i am sorry