Do Slaps and Spankings Hurt?

At Rome's Children's Museum, Explora, there's a ramp dedicated to the rights of minors.

Under the title 'Children's Rights in Simple Words,' a series of articles are on display, taken from the United Nations Convention on the Rights of the Child (approved by the UN General Assembly on November 20th, 1989.)

One of these articles really troubled me, because I believe it is a right that continues to be trampled on in our society. This is the simplified version the museum has drawn up for the kids that visit:

ARTICLE 19:
"No one has the right to hurt you. Adults must make sure that you are protected from violence, abuse and neglect. Not even your parents have the right to hurt you."

Well, let me ask you this: Does it hurt to be spanked? Does it hurt to be slapped?

It might not be comparable to the treatment to which children in war zones are subjected, but slapping and spanking does hurt (not to mention the emotional harm that it does).

So what right do parents have to do that?

Furthermore, how on earth do they justify the fact that when their child hits another kid, he's told off ("Timmy! You must NOT hit other children, we don't DO that, ok?") but they, the adults, can hit him if he misbehaves?