What a moron. Even if the clerk had given him the "drunk with guns" discount he wanted, what's to keep him (clerk) from waiting until the guy goes to the room, then calling the cops and giving them a key to the room so they can go in and arrest the drunk while he's sleeping?
That's what I would do if someone pulled it on me. Though it could be more dangerous for the cops if he were holed up in the room, so I'd try to stall him as long as possible. Give him a room that makes him walk as far as possible, and make a dummy key so he has to walk all the way back after finding out it doesn't work, then apologize and fiddle with the key programmer, say it's not working and to hold on for a minute...
Why yes, I have stalled people for the police before. (Though fortunately, they were unarmed in those instances...not sure how long I could keep my cool whilst staring down the barrel of a gun.)