Well, if they built the parking with the apartment I see no problem in the landlord charging tenants for the spot and letting them sublet it with the help of the landlord. If you didn't want the spot with the place, should've chosen another one.
There is all kinds of stuff wrong with this statement.
A) It was the only apartment complex that met my needs.
B) I don't think there were any apartment complexes where a parking space was optional.
C) As I said above: I had a car when I rented the place. I gave it up later. That was not in my plans at the time that I rented the place.
Without commenting on (A) or (B), surely (C) is not a reasonable complaint? If you rent a 2-bedroom, but then your roommate moves out, then certainly it was not in your plans at the time that you rented, but just as certainly you wouldn't expect your rent to go down. (I recognise that it's a different situation, since no-one can readily use the other bedroom, whereas someone can use the parking space; but what I mean is that "That was not in my plans" is not in itself a justification for a rent abatement.)