I was less “applying” and more observing the way this “rule of thumb” conforms to many people’s moral intuitions, and its possible implications. I’m not denying that at the older ends of the scale there comes a point at which increasing age does not mean decreasing vulnerability to exploitation. For example, I wouldn’t say 35 and 55 is an immoral pairing, despite violating the equation.
I’d be weary of applying these kinds of “rules of thumb” at extreme ends of the scale.
I was less “applying” and more observing the way this “rule of thumb” conforms to many people’s moral intuitions, and its possible implications. I’m not denying that at the older ends of the scale there comes a point at which increasing age does not mean decreasing vulnerability to exploitation. For example, I wouldn’t say 35 and 55 is an immoral pairing, despite violating the equation.