What is this dealership trying to do???

I agree with bigdogger somewhat. Is 2 or 3 hundred bucks worth screwing up the goodwill factor with the dealer. Consider how much you will use the hitch. How hard will it be to sell and what will you get for it? Then consider what your goodwill with future warranty work is worth. I'd try to barter some parts or merchandise for the hitch, if you just get some toilet paper for it the goodwill could be priceless. I'd let them know in a subtle way I am doing them a favor, I don't have to give them the hitch. If they were to get nasty I'd keep the hitch. No goodwill exists or ever will, all they care about is money.