By that logic, no one should be spanked, paddled, or flogged. If it hurts, even welts or bruises... it must be abuse.

Of course it's a kink... and why would you invalidate the legitimacy of those who like being taken down a notch?

And let's not forget the root of the word. Humility. Humble.

Just as some people enjoy being forced to submit sexually... some people enjoy being "forced" to be humble.