I understand your frustration, having had similar experiences with Class 01 FFLs who wont honor a C&R FFL or who will only receive a firearm from another FFL.
That said its the right of every seller to condition the sale of some item of his property with whatever lawful terms he wants to sell on. He can require shipment to a FFL, or that payment is only in the form of a USPS money order, or even something really silly like payment be postmarked on a Thursday.
Its his property and he can make it as hard or easy as he wants to find a buyer.
The buyer, on the other end of the transaction, knows before buying what the term and conditions of sale are. Complaining about those terms to which he has agreed by placing a bid seems to me to be, well, call it about as reasonable as the terms he complains about.
