Hypothetical question: Your 21 year old son lives at home with you and your husband?

You are a Christian and you are very devout. Your husband is not and your son is rebellious in his faith. He starts bringing home his girlfriends and having with them in his bedroom. You know this because their noises are disgusting and you can hear them from other rooms. You tell him he must not do this. You say he may bring his girlfriends home and sit in the living room and watch t.v. or visit or something but this type of behaviour is not o.k. in your house and if he insists he must go somewhere else. He says too bad I am doing it anyway. Your husband supports your son. What would you do?