Because I have listed several sources backing up my statement with examples showing current sports professionals claiming (and in Keane's place even confirming) that this kind of practice is common.
Watch the replay tonight; if they show it in full with the slow motion from all the different angles as was shown in the stream, you will see it was a hurrendous challenge and could only possibly end in an injury to the receiving player. There was no possible way Dunk could get the ball, neither was his tackle anywhere near the ball, and the tackle began before the player even had received the ball. I suggest due to the timing of the challenge coming fairly soon after half time, it was made in response to a need to be more physical to compete with Doncaster's physicality, which had dominated us in the first half. Is that not feasible?
You're confusing two different things. Yes, sometimes professional footballers go out to give an opponent a whack. It happens.
But you've been claiming you know for a fact that this is what happened in this case. Unless you were in the half-time dressing room you can't possibly know that. And you weren't even at the game were you?