Don't worry, happened to me on wed. (well not exactly like yours) I did feel Like they were treating me like a kid.....you know what you should do, go buy a scratchoff, tell them "I have money with me" and after they sit you down and process your papers then ask for your card, pull out the scratch off and say "what ever I get on here is my down payment"
that'll teach them......ooorrrr you could just key all their cars....VERY deep.....