Yep. What's sad is that no matter what happens, a good working relationship is destroyed. Those are hard to come by.
I don't think he should threaten to quit. I've never been an advocate of that. Best case scenario, he makes the threat and they give him what he wants. Except now no one trusts anyone. They'll feel victimized/strong-armed (even though they deserve it) and wonder if he'll do it again to them. He'll wonder if they just bought themselves time so they can lay him off or fire him outright.
What he SHOULD do is have his conversation with them today, but without threats of any kind. No ultimatums. Even if they ask "if we don't do this for you, will you leave?", you don't stoop to that. You just say "I think this is an appropriate step for someone in my position doing the work I'm doing" and leave it at that.
If they don't come through for him, then he needs to find another job ASAP and quit without entertaining a counteroffer. If they do counter (which they probably will), you just say:
No thanks. I appreciate the offer and the time I spent here, but we have different goals and I think it's best we go our separate ways.
If they have half a brain, they'll see that for what it is: You fucked me and thought you could get away with it. You were wrong. You get to have your jab without being a dick/unprofessional.