In order to demonstrate "diminished value", you would need to prove that the car is worth a specific market value if it had not been damaged, and a specific, lower market value if it had been damaged and repaired properly.
The fact of the matter is, a car that has been in a minor fender bender and repaired properly really isn't worth any less than a car that hasn't. Thus there is no diminished value.
Just make sure you get the car fixed at a top-notch body shop that is qualified to work on the NSX. Once it's fixed, don't agonize over it; it will be good as new.