Taysom Hill out for the season with torn ACL-additional damage per Rapoport [Hill placed on Injured Reserve on 12/6]

I haven't seen the game yet, but that is an absolutely horrible tackle. I hope he was flagged/fined....etc.
Not taking up for the guy, well maybe I am, but where are defenders supposed to hit? Meaning even for our guys. They go high to the head, flag and fine. When I played football, I was always taught to go low. I mean, I hate it happened for sure, but where are they supposed to hit someone?