Umm... Yeah... Duh...

That's my response to Belle Waring's question

What does it mean to "have the mental age" of a 12-year-old? Should you necessarily have the sex life of a 12-year-old, for all your days?

If you accept the "mental age" diagnosis (highly problematic, but that's an entirely different discussion) what possible alternative is there? I try not to be dismissive when I respond to posts, but this is just a no-brainer. We progress, once again, from the principle of consent: legitimate sexual activity between two persons requires the consent of both parties. Assume that a 12-year-old, or equivalent, cannot consent to sexual activity? Anyone want to debate that statement? And before you start quoting Nabokov at me yes, I realize there might be some edge cases, but on the average? Ok, then we have consent by proxy? Anyone want to go down that road? Uh-huh... thought so. As a side note to a nut, who posted a comment asking

Who gets to decide which woman/man with a mental/physical disability is "good enough" to have children? Isn't that getting back into the dangerous grounds of eugenics?

Nope, you can intelligently advocate that position without resorting to anything which smacks of eugenics. One of the duties of being a parent is assuming guardianship of your child. Anyone who is incapable of being their own guardian (which would seem to be a key component in any reasonable definition of mental disability) is likewise incapable of assuming guardianship over a child. QED, unless you intend to support the position that people have a right to bring a child into the world without assuming the concomitant responsibility of raising that child.