Unroadworthy vehicle

I was provided with a vehicle that was not roadworthy. A nail was in the tyre that neither Europcar or I noticed at the time of rental but the car was provided in this condition. This is a case of my word against theres and now I appear liable for their (human) error. Even the RAC commented on how they tend to turn cars around with improper checks. It appears that I will now be liable for the replacement tyre and associated costs. I refuse to accept this as they provided me with a car that potentially put my life in danger. I will never use Europcar again as the attitude is to place blame on the customer and not perhaps their sloppy servicing of vehicles.