It Couldn't Happen to a Nicer Guy(1974)

When Harry Walters runs out of gas, he gets picked up by a beautiful young woman. But when she pulls a gun on him and orders him to take his clothes off, Harry puts up no resistance and is sexually assaulted. He reports the incident to the authorities, but they either don't believe him, or, if they do, can't understand why he would consider it a crime - a reaction he also gets from his friends and family.