I liked this article. It says what you're thinking, without saying "this is what people think."

Example: "Maybe we accept that 19-year-olds are not yet fully responsible adults for the purpose of driving a rental car, but hey, we still need someone to drive our tanks in Afghanistan."

Edit: To clarify, I'm believe the above example shows that we see there is a problem with what you can do at what age, rather than the surface meaning of the example.