Though it's really hard to overcome Gavin's continued unwillingness to retract his endorsement-- I think doing so requires enough of everyone else to sign on to make it clear that he's alone (or close to it).
Has anyone tried authoring an open letter to Gavin, requesting that he makes a revised statement? And then members of the community could sign it. I'd imagine we'd get quite a few signatories. That would be a start, at least.
No one can make Gavin officially retract his endorsement. Tin-foil hats on, JUST A THEORY, but I believe he could actually have been a CIA mole, or turned into a mole when he visited the CIA headquarters in Langley. His actions, by dividing the community through Bitcoin XT, also supports the theory. It was the basic Divide and Rule strategy.
It's probably better to invite other Bitcoin Core Developers and have their opinions, like Eric Lombrozo? Luke Dashjr?