The best solution would be to just reverse the downgrade, and have ThePHD deliver the keynote. Send a strong message that there would be a major fallout had the Rust Project committed to their internally-made decision, but give them a chance to actually do the right thing. But that's presumably not happening, because ThePHD already left the presentation without giving them a chance to respond.
I also think the "Rust logo" controversy was over-exaggerated, since they didn't actually implement the copyright but only proposed to. And the entire mod team resigning made the mod team look bad, at least initially, because they didn't even really explain why.
The bright side of this over-reaction is that it's going to get some response from the Rust Project. Because apparently strong words are the only way to get a closed-door organization to respond appropriately. They'll post some sort of apology, and maybe it won't just be words, but they will actually become more transparent in a way that guarantees this will never happen again. Like how they all but walked back the copyright proposal and re-structured the core team following mod team resignation (or did they?).
But that's not an excuse. This sort of drama is toxic, I honestly think more toxic than the original action. Like, I feel bad for whoever made the anonymous decision to downgrade ThePHD's keynote, because even though it was wrong and hurtful, it doesn't deserve this level of vitriol. There needs to be better a way to get change than over-reacting to every mistake.
I really do hope the Rust project becomes more transparent, not only to prevent the situation from happening in the future, but the response. If everything has community input, when bad decisions happen the community can only blame themselves.