They should have dealt with it earlier if possible. (I assume operations told them they needed to transport a flight crew after the airline was already boarded.) Given that they didn't, someone should have had the authority to offer enough compensation to get someone to voluntarily deplane. I have trouble believing that if they offered $3K or whatever, they wouldn't have been able to find another volunteer or two.

That said, refusing to follow the instructions of a flight crew and creating a scene is not going to end well for you however convinced you are in the righteousness of your position. (I have been bumped off a flight after I was onboard and sitting down. It was years ago and I don't remember what the exact circumstances were if I ever knew.)