Not everyone was cheering, but the drunken idiots that were cheering were doing so loudly. I'm not certain they were cheering about Duncan anyway, for all I know Ichiro was throwing out T-shirts at the other end of the arena. Besides, it seemed pretty obvious the injury wasn't that bad from where I was sitting. The booing when he got up and started walking back and forth was because 1. He was writhing on the floor for about five minutes and was able to walk it off after about ten steps, and 2. The Spurs didn't have to call a timeout and weren't pegged with a delay of game when he was pacing back and forth. There was quite a bit of applause too when he did get up, which nobody seems to mention. I think the bottle was thrown at the refs who were huddling in front of the Spurs bench for some reason.
And the crowd was loud, incredibly loud. The refs took the crowd out of the game in the second quarter with too many whistles, but got the crowd back in the game with even more whistles. By the time Wilkins was called for an offensive foul for daring to attempt to dunk on the Spurs, the crowd was at a near riot level. I wish the Key was always that loud, well, without the drunken idiots shouting expletives and whatnot. There's a whole demographic in "Drunken Idiots" that the NBA needs to figure out how to dump, and quickly.