It was a bad tackle, worthy of a red, I think he even admitted it. But the truth about it is that it was accidental. The amount of times he clears a ball with a high foot is unreal, but he does it as nobody is normally there, such as in the build up to one of Robben's chances. De Jong obviously didn't see Alonso coming, as he isn't that kind of player. Yes he can be reckless, but he is professional about it nonetheless, as we have seen week in and out for us.
Cantona on the otherhand delibrately assaulted someone, big difference...