We'll see what specific laws the disciplinary committee use for Payne's hearing, but they are likely to be from 10.4 "Dangerous play and misconduct".
So there are no less that 3 different references to interfering with a player off the ground being dangerous - how many do you need?(e) Dangerous tackling. A player must not tackle an opponent early, late or dangerously.
A player must not tackle an opponent whose feet are off the ground.
(i) Tackling the jumper in the air. A player must not tackle nor tap, push or pull the foot or feet of an opponent jumping for the ball in a lineout or in open play.
(j) Lifting a player from the ground and dropping or driving that player into the ground whilst that player's feet are still off the ground such that the player's head and/or upper body come into contact with the ground is dangerous play.
The collision between Payne and the player with the ball still counts as a tackle, albeit an illegal one.
There is really no debate that it is dangerous play - the only point of discussion is the degree of punishment. There aren't hard and fast rules as to what would be a penalty and a caution, a yellow card and a red card, so this is up to the referee's training and judgement, "case law", instructions from the ruling body and the like and a different referee may have applied a different punishment.