Clearly he was responding to KG's hard pick earlier. The difference was KG just put a little extra on a pick fluidly, while Hamilton had to go out of his way to reach up at KG's face with an elbow as an afterthought while passing.
Honestly, as Van Gundy pointed out, the game was lacking any chippiness, so it was good to see a little fire between the two teams. Though I'd be plenty happy to see Detroit take it on the chin silently all series, I've got to believe they're going to come out with some intensity at some point in this series.