>If only this were in any way true.
It's true in the ways that are pertinent to this discussion. Another poster equated speech with assault. I would guess most with that worldview haven't spent much time being assaulted in the physical sense.
No one is saying that words don't have significance or power. The point is that, in a very literal way, words can never hurt, physically hurt, those who hear them. The listener has time to collect their thoughts, understand the circumstances, and choose an interpretation and a reaction. We hope they will choose healthy interpretations and reactions, even if the original speaker did not.
Meanwhile, a victim of a true violent crime like a mugging, carjacking, or politically-motivated beating doesn't have time to think down the road about how badly someone's words hurt their psyche, because they're busy bleeding and dying, in the literal sense that their body may permanently cease to function, if they aren't treated within minutes or hours. They were attacked without choice or option, and their body is reacting to the physical realities thrust upon it, and all the victim can really do is try to remain optimistic about things.
Yes, it is sad when someone is bullied or otherwise made to feel bad about themselves. But it isn't anywhere near the same thing as a person who has undergone an actual assault.
The saying really is not really hard to grasp, and it's widely applicable. That's why it's a tired old cliche. :)