I think he raises a good point. What he means is that there's no basis to believing that those 9 year olds using the word rape in common practice will mean they will be more insensitive to the actual rape subject, or that it will make the word lose it's significance when used in it's original context. It makes perfect sense for me.
I have the impression I hear a lot more jokes about paedophilia these days than I used to hear a couple of decades ago, for example. When I hear one I usually don't appreciate it much and generally find them distasteful. However, I'm pretty sure the person saying it, and society as a whole, are a whole lot more alert to the seriousness of the issue than they were 15 years ago.
Above all, I think it's a simple matter of elegance in speech. I think the practical consequences of the usage of these words are being vastly overrated.