A dogs claws will not scratch the paint down to bare metal. They will leave a mark that easy enough to buff out. However, the pads on a dogs paw can and often does pick up various types of grit and that can scratch right down to bare metal.
But the neighbor still needs to provide evidence of the deed, not just an accusation. Even if he can prove that the dog was trying to climb on the hood in a panicked state, what caused the dog to panic. If a person did something to panic the dog, then that person could be held responsible. But then, are you violating the leash law? That could be a factor too. This is how lawyers get rich.