I personally don't think it's a good thing to chase Gmax or other specific Blockstream devs away from Bitcoin, even if that could be done.
Consider:
If we are right in our position, many people are going to have to do some fundamental rethinking on Bitcoin governance and perhaps even some soul-searching on their position overall. This could mean bruised egos and all sorts of things. Some might even consider quitting entirely. If done wrong, this means losing exceptionally valuable talent, at least in Gmax's case, or worse he could begin to use his sway to really mess with things out of spite. Another bad outcome would be him merely isolating himself so that no further inroads are possible.
The optimal outcome is of course that the devs stay on but gain a true appreciation of Bitcoin's multi-disciplinary nature and the limitations of the scope of their knowledge (i.e., that it mostly doesn't extend to incentive design and economics), or at least stop assuming the opposite. I think I saw Gmax directly acknowledge the importance of this in response to
@Peter R the other day.
To avoid the unwanted ego effects, in the case where someone looks to be reeling from having someone raise a point they didn't know how to counter and that called a lot of what they thought they knew into question, I think a careful application of "
kiss-kick-kiss" is most effective. Amiable debate, ruthless banging on the key points they are clueless about, then
heartfelt praise for the things they are great at.
This is how to change minds...because the hard part about changing your mind is the pain after you realize for a moment you may be wrong, which people immediately turn to cognitive dissonance to get away from.
Ease that pain yourself instead, as you who wrought it are uniquely positioned to do, and then they can more easily see their error with a clear mind.
If Greg is really reeling now, the best thing to do is, if there is any opportunity to do so at all, point out an excellent observation he has made or whatever. Keep him in the game.
If Core/Blockstreamers are being arrogant in one-on-one debate, by all means bang away! But once they do feel the heat and start showing the signs of retreat, be nice to them. You can always know if an argument isn't getting through, because they will just ignore you, not retreat nor isolate themselves nor fire back with their best nuclear-authoritative tone. Since it's counterproductive to keep banging on them once they already have shown that they both (a) have never considered the point and (b) find it important to consider, which is how I take Gmax unsubscribing mailing list (assuming it's not coincidence), easing any ego damage becomes first priority IMO.
Then commence the next wave of banging!
I've seen before several times how a group like Core/Blockstream actually ends up changing their position. What happens is without really acknowledging it, the key figures just capitulate in an oblique way, then everyone else quietly falls in line, with the lower-ranking True Believers often slinking away completely, their
raison d'etre lost. For example, we may start to hear things from Core/BS like, "Well we believe XT is on the wrong track, but may the best implementation win! <snicker snicker>" A kind of backhanded acknowledgement smoothed over by some humor, and their past "XT is an attack" and "XT is an altcoin" is never spoken of again. Same applies to BU of course. Then they will have acknowledged the basic validity of multiple competing implementations.