A married couple spying on their teenage son via a special computer program, start finding out the details of his interest in sex.
Here's an extract from their dialogue that puzzled me:
“Talk to him,” she said.
“I have,” Mike said. “I’ve explained the birds-n-bees. I’ve explained that sex is best when blended with love. I’ve tried to teach him to respect women, not objectify them.”
“That last one,” Tia said. “He’s not getting that last one.”
“No male teenager gets that last one. Hell, I’m not even sure any male adult gets that one.”
(Harlan Coben,"Hold Tight", chapter 5)
What has puzzled me is "that last one" phrase which doesn't seem to be used in the context of actual cases of sexual intercourse -- all that was said before is that their son watches online porn.
So what "that last one" means in the context is unclear to me. Could anyone explain what it stands for?