I'm a little late to the party, and it sounds like you've arranged a decent resolution. I am not suggesting that you change a thing at this point, so long as things continue to be cool with the building's management. A couple of things to keep in mind in case this comes up again, though.
(1) I don't know what state you live in, but I have a great deal of difficulty believing your state's laws permit the landlord or his/her/its agents to take such "self help" measures as removing your rack or car under these circumstances.
(2) Does your state have small claims court system? If you are in California, the answer is "yes." No lawyers, available to resolve matters up to $5000. That would probably cover any damage or loss to the rack, and probably to the car, assuming these folks suddenly decide to be Neanderthal about this. Don't threaten this up front, but if they try the strong-arm "we're going to take your stuff" approach again and won't be reasonable next time, trot that one out. (Believe me, as a landlord/manager of an apartment complex, they will understand about small claims court).
(3) Document, document, document. Take photos showing you are not blocking anything and/or that there is plenty of room for someone to get past your car & rack. It sounds as if the claim from the management was that your car + rack was interfering with other tenants' use of the driveway/carport area. Your photos would need to document that there is plenty of room for other cars to get by. Measure how much space is between the back of your car + rack and the far edge of the driveable surface of the carport/driveway area, the same distance when your car is not there, the same distance from the monster SUV's you found, and from the cars on wither side of yours, and photograph the measuring tape readings. Keep these in your sole possession for now for possible use later.
(4) Do a reality check. Compare the measurements you took for (3), and make an honest assessment of the distances involved relative to the width of a car or pick-up that would have to get past where your car is parked. Consider how these numbers will sound to a third person who knows nothing about your situation - such as, say, a small claims court judge. Maybe even ask some of your friends or co-workers what they think without letting them know which side of the dispute you are on. The point is to get a sense of how reasonable your side of the story will sound to someone else, which means that it does you no good if you stack the deck in your favor when you ask for other people's thoughts. This will, in turn, give you a much better sense of how hard you can push your side - or, if need be, how far you can carry a bluff against the management. Knowledge is power - primarily the power to make informed decisions, and the power to distinguish between a calculated risk worth taking and bone-headed move than can only end in disaster.
I hope you never have to make any practical use of any of this. But if nothing else, you have learned that you do not have to just cave in when you get one of these "f*** you, worse to follow" letters.