Just watches the replay on TV, including all of the slo-mo from various angles. Blackshear is boxing out Carter, who is behind and to his left (outside). Carter reaches across Blackshear with his left arm and pushes him away from the baseline to go after the ball. As Blackshear stumbles back from the shove he reaches out and grabs Carter.

So Carter actually fouled Blackshear trying to go after the ball. You can't complain about one without equally complaining about the other. Two guys jostling for position to get critical rebound at end of game, good no call IMO.