Small island Hire company charging me £75 for a small scratch on the car I hired (scotland)

Location: Scotland.
I hired a car from a Hebridean car hire company mid June for a few days, they messaged me two days later saying they spotted a small scratch on the tire and they are charging me £72 for it. Are they allowed to do this? I paid a small fortune hiring that car for two days and insuring it (any damages up to £250 go down to 0- excluding window or wheel damage) . Surely this is all part of the wear and tear of a car and isn’t structural damage? Just sees insanely petty to me. Is it mandatory to pay this and what are the consequences of not paying? this?