I agree with you that paddles or switches can be used for "spanking", and that "spanking" is a form of "beating", but still the words are different. "Spanking" strongly implies that it is done to cause pain without serious or permanent injury. "Beating" has no such limitation.

I agree that it is not the right way to discipline a child, but I can recognize this distinction in meaning.

I find this interesting, actually, as a form of argument. The annihilation of semantic categories. It's like argument via Sapir-Whorf.