Help...Visitation Concern

I have sole and legal custody of both my children. The 11 yr old girl no longer wants to visit her father, and cries and pleas with me not to let her go. The Divorce Decree states he gets visitation rights, and I would love to see him involved w/ the kids; however, this is the Problem:
My ex is living with a woman...he does not monitor the children, and hence they see stuff they would never see at home (ie bad movies, her naked, bad language, etc) My daughter is also upset because she has no room to call her own and they gave her a 3 hour lecture with a 14 page letter telling her what is wrong with her. To make matters worse, she has seen and heard stuff that I don't find appropriate. She has even started asking me questions about sex right after she comes home from visiting him. I have tried to talk to my ex, but he will have NOTHING to do with me (because he blames me for destroying the family) He won't answer letters, emails, phone messages, NOTHING. I sometimes wonder if he is deliberately trying to pay me back thru the kids. Nonetheless, I want to protect my children what should I do?
PS My daughter ripped up pictures of her dad last night, saying she hates him.

Do you still have the letter ?.

The way you describe it, it is bordering on child abuse and neglect. I can not help you on the legal aspects as what I would do and what is legal are two seperate things... first off, I would stop all visitation and bow to my childs wishes about not visiting.

Then I would see an attorney and either be the one to initate court action.. or get ready to defend against his legal action..