Note how Person B makes a point to mention there are many good-hearted teachers who would not attempt to abuse their power in such relationships, so they shouldn't feel this absolutist law is aimed at them. How nice to make that clear. Yet because the law is so non-negotiable and absolute, without even bothering to ask for an investigation, or even if there is any plausible reason to suspect foul play, before dragging someone "downtown" these good-hearted teachers are going to be punished along with any bad teachers. And all on that infamously draconian "erring on the side of caution" schtick. So they are effectively delivered a slap on the face after that disclaimer of consideration.

Any law that is absolute like that, and doesn't even call for an investigation or ask any relevant questions about the situation, is bound to hurt numerous innocent people! No law in a truly democratic society can be so absolute, nor should we be willing to tolerate a law that we know is going to hurt many innocent people just to "make sure" the bad ones end up getting punished. That is supposed to be the very antitheses of the American system of jurisprudence!

No law must ever be based on assumptions alone. All laws must be contingent on substantive evidence and executed on the basis of plausible cause for concern.

Now note the disclaimer made by Person A that we can "all agree" that there is no way a 12-year-old girl could possibly give consent to a 40-year-old teacher, but it's "different" with a woman 18 and over, because... she is a legal adult. I would have sympathized if she mentioned the legality issue, and how a 12-year-old is not allowed to give consent; otherwise the statement goes from the legal realm to one of belief and moralizing ideology, but not established incontrovertible scientific fact. By leaving that out, Person A made sure to frame the statement in a very specific and PC manner.