He went back to his truck and brought out a Snap On 6 point socket and it spun the bolt out with no problem. The bolt head was a little rounded, but the Snap On socket gripped it firmly. When he left, he let me hang onto the socket so I could finish up the job. He also suggested I get some some 6 point sockets of my own.
Later that day I went to Home Depot for some stuff and picked up a Husky 14mm 6 point deep wall socket while I was there. When I got home, I noticed 2 things that were different between the Snap On and the Husky.
First, the Husky has a tapered opening. The actual gripping walls of the Husky socket do not extend all the way to the open end of the socket.
You can the difference in these 2 pics, although I think my socket has an even deeper taper than the one in the picture.
The other difference was how much tighter the Snap On gripped the bolt head. Holding the socket on the bolt head, there was considerably more "wiggle" with the Husky socket vs. the Snap On.
Even though both brands carry a lifetime replacement warranty, the quality difference was readily apparent. I can certainly see why a professional would spend the extra money on the Snap On tools.