Good, Bad, and the Ugly.

[theaardvark]

At the game and on the jumbotron, it really looked like he grabbed the shoulder and dragged him down, not pulled him back.

It looked more clear on TV.

Direction of tackle is no longer relevant, you can pull them forwards, sideways, any direction, but if your point of hold is above the namebar, it is a horse tackle.

[Jesse]

Yes, there are several shots which clearly show it was a horse collision infraction.    What surprised me was MOS challenging the call and losing his timeout....not that it really mattered with a 50-14 score.    There was also a horse collar tackle on KL89 which was accurately called.  
Perhaps MOS will explain why he challenged the call on the Coaches Show

He already did.

Said he thought it looked clean and that he held his flag in his pocket during the first game against BC on some times where he shouldn't have and didn't want to make the same mistake again.