In last night's NBA Conference Finals game, LeBron James blocked Terry Rozier in what was a highlight play of the game.
https://www.youtube.com/watch?v=d5XgkH-7faY
As Rozier goes up, there is nothing between him and the basket. James jumps in front of him, and Rozier's momentum causes him to make contact with James' left forearm but not his body. Meanwhile, James' right arm reaches up to block the ball at the peak of Rozier's jump. The initial contact is with the ball, knocking it loose from Rozier. The momentum of Rozier's arm leads to contact between Rozier's arm and LeBron's while Rozier still has his hand on the ball.
Was it a clean block or should it have been a foul?
(EDIT: Apparently I can't fix the typo in the poll question.)