This isn't going to be popular around here, but man, that looks clean to me. Watched it seven or eight times. I dunno if I'd have overturned the call on the field because it's very close, but I'm a lot less angry. The main thing is, when contact is made, Shrader's head keeps going forward while his body goes backwards, then his head snaps back after. So that means that there was not helmet-to-helmet contact initially, Shrader's helmet snapped into Mascoll's.
Sure looks like a form tackle, shoulder into the chest, helmet tucked. Only way it's targeting is if he launched himself or crouched down and extended, but from that angle it doesn't look like it at all.