That jumped out at me too. I don't know if a double standard towards sex was the root of it but I've never heard of anyone getting the cops to go away like that.
It's easy. Ask the cop if he has a warrant for your arrest. He/she won't or they wouldn't be asking to speak with you. When it is obvious they don't, tell them to get off of your property and shut the door. Never, ever, allow them inside without a search warrant or step outside "for officer safety". Tell them if they don't feel safe, they can leave; and then shut the door.