It was a head clash. Barely a yellow card. Very sad for souths 13 though. 12 weeks? please..
Under World Rugby guidelines (see attached) it's a clear Red I reckon.
First of all - it was a "High Tackle" as there is clear contact to the ball carrier's head. We can't deny that.
Next - The contact with the ball carrier's head was in contact with the tackler's head (at least)
Next - it was High. So it looks like a Red Card.
Are there mitigating factors? Well first of all it states that as it was in open space with a clear line of site for the tackler with time before contact, then these mitigating factors hold less weight. Regardless....
The tackler didn't change his height.
The ball carrier didn't change his height
The tackler is not unsighted
It was not reactionary, nor was their clear release
Clear initial contact with the head (by the head).
It's about as clear red card as you can get.