I am not sure it is serious foul play or violent conduct. He was in control the whole time and the tackle had no more intent to injure than any other tackle trying to get the ball from behind.
I have certainly seen worse tackles been given a yellow / less.
How can you get the ball from behind while swinging yours legs from behind when there are two solid legs in front of you?
Why does that factor into the decision as to colour of card? Red cards are for serious foul play or violent conduct. THis was neither, it was a cynical challenge that is worth a yellow in every other game where I've seen a similar challenge made.
Those type of tackles can put a player out for life.
Reality is that ' smart ' players don't make those sort of challenges.I think it was serious foul play.