I am struggling to understand why this is even possibly a YC. Based on the way you describe it, no play on the ball, intentional, and violent, possibly injury causing. No different than if he had stuck out an arm and clotheslined the guy. I had something similar a couple of seasons ago. White had ball stripped from him, chases Blue all the way up the field. Blue makes a cross and White continues his run and same thing - lowers shoulder and took him out. I had him on RC before the kid hit the ground. This play was called out in our group meeting as being a situation where the ref (I was not mentioned) was brave enough to give the proper RC. Apparently, it is rare in our association.