In a private driveway someone backed into your car while you were parked and their insurance company says you are part negligent any suggestions?

Fight it! If the driveway was yours, then the other person had no business driving there. It does depend on what the reasons were. If you were parked more than 12 inches from the curb, then that is neglegent - it is law to be within 12 inches of the curb (never more). So find out why and keep all evidence. If you have to take that person to court, do so.