Car rear bumper got ripped in car wash. Car wash claiming not at fault. Options?

This happened in Redmond, WA. The automated car wash essentially almost ripped my rear bumper. They claim they are not at fault since there was prior damage already present. What are my legal options? I have already filed a claim with my insurance.

Edit: I have no idea what happened while in the car wash. The rear bumper was pulled from the passenger side and there is a tear on it since rest of the bumper stayed on. That's the reason I say almost. This happened in brown bear car wash.