The threats from Letts are laughable. Sure, Avis can cancel your reservation or blacklist you - but corporations do not prosecute people, only the government has the right to do that - and using a discount code you're not entitled to is not a criminal offense of fraud, unless you use the code to avoid paying for damage to the car (i.e., it includes LDW) - and even that would be hard to prove and likely very low on the list of priorities for any urban prosecutor's office.

Maybe Avis can sue you - but is this really the correct way to handle it?

So, let him blow his fire and brimstone - the only real risk any of us have is losing a reservation or getting blacklisted from Avis. If they want to get rid of me as a customer because I'm using a code that saves me $5-10 a day and got my business instead of it going to a competitor, well they are dumber than they appear to be.