I'm sure you will find no shortage of Argentine lawyers willing to bill you in US dollars for pursuing a case in an Argentine court that will go nowhere. You are less likely to find an American lawyer willing to sue in US courts because an email from a hotel employee in Argentina is NOT binding on Marriott corporate in the US. (it's probably not a binding contract or "promise" anywhere in the world)

I suggest that you calm down and take all of your hotel business elsewhere if you don't like how Marriott customer service operates.

And next time, be more open to the concept of points as compensation. It works better for all involved. The only question is the number of points you deem to be equivalent to your financial "loss".