I don't know, I read both of the other posted links to get a different perspective. IMO, the NY times article seems written with gathered, second hand information. William Shunn seems the most reliable, in the way he was there for the pyrotechnics. The original writer claims he was in the room before Shunn to witness the sequence of events, though he says he did not hear the Peacock/Costello exchange.
I don't know much about Peacock, other than some recordings that a friend has (world class skills). I'm not a fan of Elvis Costello, but I'm hoping Mr. Peacock had some other reason for not wanting to play, and that it wasn't that the material or the artist was 'beneath' him. It was supposed to be one or two tunes, and a sort of thank you with the BD cake and all. Seems kind of egotistical and mean spirited.
On the other hand, we don't really know what went down and Mr. Peacock could well have had a good reason for doing what he appeared, by published accounts, to do.
As a hired bassist, IMO shouldn't you try to do whatever is asked? If it ends up you don't like it, you decline future gig offers. It's like we're missing some vital piece of information that might shed some light on this.
Oh well, lunch is ready!