Why does it matter?
VIOLENT CONDUCT
Violent conduct is when a player uses or attempts to use excessive force or brutality against an opponent when not challenging for the ball, or against a team-mate, team official, match official, spectator or any other person, regardless of whether contact is made.
In addition, a player who, when not challenging for the ball, deliberately strikes an opponent or any other person on the head or face with the hand or arm, is guilty of violent conduct unless the force used was negligible.
This was clearly not negligible which makes is as clear a red card as you’ll ever see, yet the nuances always come out to explain why simple, letter-of-the-law, decisions don’t go our way while others get off on such technicalities.
Any referee that is for a system where you can watch video evidence of a missed off-the-ball incident and deem that the fair outcome is a drop-ball to Sunderland is simply dishonest and not adhering to the rules, thereby making them unfit for the job.