As I looked at the picture, the first thing I thought was "but that's a burn. Did someone spill a chemical on his paw???" and then, reading through the rest of the thread, I noted that your newer vet indeed thought that as well, but considered it unlikely.
It really struck me as a chemical burn...and those kill skin just as fast as a heat burn. And the skin will peel off, growing back from the inside and peeling/sloughing off (and moist, rather than dry peeling), on a topical burn. It's that red color which got me thinking about that, because I just couldn't justify anything making it red. If the circulation was cut off/disabled, then his skin would have a pallor or a lack of color, rather than being raspberry red. That red...to me, man, that's something which hit him outside his skin.
Know what I'd do? I'd see another vet, with those photos, and ask him if there is anything which would cause this. Get another opinion as to what happened, and bring in the photos as a demonstration. See what someone who doesn't have connections to the clinic says.
If in fact there was a burn, then I'd likely get the authorities in and investigate them somehow. If what I think happened, likely it was just a stupid accident, rather than deliberate/intentional. Someone may have accidentally spilled a chemical or the like, or left a spill on the table, and Red's paw got the brunt of it.
BTW, anesthesia is incredibly painful if you don't have a numbing agent mixed with it. I have an allergy to novacaine/lidocaine, which is commonly used to mix with the anesthesia as the numbing agent. I had a surgery just about a year ago without any numbing agent (we had to move rather quickly, an "almost" emergency) and there was no time to search for and then remix another numbing agent in with the anesthesia. I went under in so much pain (and that was after sedatives) that according to my Dr. he knew I was out because I stopped screaming. So yes, there is pain without a numbing agent from the anesthesia, and it's rather scary.
I really don't mean to be a downer, but I just wanted to share my thoughts and experience.
Best of luck to you-