There are precious few moments in a basketball game where one player simply shoves it down another player's face. We want to think they're more, but for every posterization, every isolation, there's always some team dynamic that preceded the play that was essential.
The thing about this play is that Pierce purposely worked a switch to get James on him. He wanted to go right at James, and really, he wanted to nail a three-pointer in James' face. So, Pierce worked the clock down, jab-stepped, then somehow found enough room to get a clear look at the rim over James' outstretched arm. Nothing but the bottom of the net.
It was a rare instance of a hero-ball shot we can all enjoy.