This isn't the first protest I've heard of, but it's the first to actually happen...and it's going on right now. From the Times:
The professionally printed message on the pink sign will urge James L. Dolan, the Garden's chairman, to fire Thomas, whose team is 7-17 going into Wednesday night's game with Cleveland. Protest organizers said two people will hold up the sign in a manner that will allow supporters to sign it.
The dentist, Dr. Art G. Nathan of Freeport, N.Y., said the idea of having a protest began a few days ago and crystallized after the Knicks lost, 119-92, on Monday night to Indiana. Late in that game, a fan with a "Fire Isiah" sign was peacefully moved out of a seat behind the team bench.
Sick! I'm still at school until late this afternoon. Otherwise, I'd be participating in this. If anybody reads this later and was there, we'd love to hear about the experience.
(Tip of the hat to the Fanhouse)