Doesn't matter that he attempted to play the ball!
By attempting to play the ball in the manner he did......endangered the safety of another player....hence the what turned out to be a dislocated ankle!
Red card as defined by the rules!
That's very referee-like of you and word for word you are not wrong. I just fail to see any danger in said tackle other than the fucker unluckily broke his leg. They are slowly but surely going to remove actual tackling from the game soon with decisions like that.