It's not a kick, it's a trip. The laws are very clear about those being two separate things (kicks or attempts to kick, trips or attempts to trip etc.) and it's part of our jobs as referees to be able to tell the difference. While I'm not totally ruling out the possibility of a trip being forceful or dangerous to the opponent's safety, I'm struggling to think of any way this could be the case without deliberately aiming the opponent towards another object.
And regardless of proximity to the ball, this isn't an act of violence with intent to hurt an opponent, it's a (un)sporting incident with the intent of stopping him getting to the ball. I accept the possibility that this could have been done in a dangerous manner that would have deserved a harsher sanction, but that didn't happen in this case. A caution for the cynical nature of the challenge is fine for me, I don't see the need to act as if this is more serious than that.
Citing Beckham is, if anything proving that point. His intent was to hurt the opponent - hence VC. In the clip above, the intent was to stop the opponent - hence SPA.