All of the elements are there for a BSB. The player being blocked can't see the block coming, and can't defend himself. The block is thrown with the shoulder, and is clearly forceful - enough to knock him to the ground, completely out of control of his movement. Is it the most vicious hit we've ever seen? No. But it crosses the line of forceful, and it what the rules makers have directed us to call, to help them change the culture in football, to get away from blocks intended for punishment rather than just playing the game. That block could have been just as effective had he put his arms out and just shoved the opponent out of the way.
Robert