The question is, if you assume for just one moment that the rental firm is operating fairly… are you sure the scratch wasn’t there when you rented the car? I’ve never rented a car without the firm giving me a damage report to sign before I drive away, and giving me the opportunity to add anything missed. If I see the tiniest scratch, I add it to that form, photograph it and send them an email before I leave the lot. And I’ve never been scammed for damage that I didn’t cause myself.