The fact that it was previously a rental vehicle does not mean that it was not also a leased vehicle. The rental company may well have leased its fleet.
Why did your friend's parents accept delivery if the car is in obviously bad condition?
They're not going to get the seller to pay for it to be inspected at another dealership, but if they feel they can prove fraud by the seller that's an important part of documenting the deficiencies in the vehicle below any standard of certification. The question remains, though, did they offer it as a "Honda Certified" used car, or as a "Dealer Certified" used car - if the latter, they may well be using their own standards for certification, not manufacturer standards.
If the seller is a Honda dealer, they should consider contacting the corporation. The dealership may not take customer service seriously, but Honda does. Unfortunately, if this was a used car lot sale and there was no representation of Honda certification, they might not be able to do anything to directly help your friend.

