When they say “consenting adult,” they mean “old enough to talk.”
You may remember the fairly recent case of Anna Stubblefield, a tenured Rutgers ethics professor (ethics!) who initiated a sexual relationship with a profoundly mentally and physically disabled man. She claimed she had learned through "facilitated communication" that he was in love with her and wanted to have sex. "Facilitated communication" meant she supported and guided his hand as "he" typed "his" thoughts on a keyboard.
When the disabled man;'s family finally took her to court, they proved to the satisfaction of the jury that she was in fact typing her own thoughts by moving his fingers, an the unfortunate man , incapable of the level of responses of even a preschool child, was being molested without being able to resist, or even comprehend what was happening.
Ethicist Stubblefield was found guilty of criminal molestation and put in prison. But here's the shocker: she is still writing and contributing to academic textbooks on the disabled, and still preaching(to at least some subset of approving peers in the ethic biz) that this was all wonderfully enriching to her diaper-clad, helpless victim.