I had a similar experience in but with Avis in Iceland, 2 years ago. They were really aggressive in trying to sell insurance so I became alarmed. They did warn me ahead that the car had several dents and scratches on. So I asked that an Avis Rep come out with me to go over the car and damages but they refused. And I refused their insurance coverage. First time I ever did this, I took pictures of the whole car before I left the lot. Sure enough, I got a bill for $3500 in damages to the car. Avis HQ was supportive with me, since I kept all pictures BEFORE and AFTER I returned the car. Avis Island did not even respond the Avis HQ once they saw all the pictures I took. So lesson is, check the before you leave and it is in your best interested to take pictures of car before and after your rental.
Another good idea, if you don't have car rental insurance on your credit card, most travel agents can sell you car rental insurance too, for a lot less the car company price.