How do you handle this issue on voir dire to disarm it?

I would be careful directly disarming any defense that hasn't been made yet. A thorough explanation of what the law is should get the point across - put it in layman terms everyone has heard of - "statutory rape, why do we call it statutory?" etc.

In just about every statutory rape case I try, I voir dire on non-defenses, and discuss that consent is not a defense, and the defendant's mistaken belief that she is of consenting age is not a defense. At least in my experience, this is a major issue that the jury can nullify over, so I also spend some time discussing why the law is this way, and the importance of juries across the state enforcing the law in the same way. I qualify the jury that they will convict if they believe the case BRD but the victim consented. Then I qualify that they will convict if believe the case BRD but the defendant didn't know the child was underage. I explain that that may be something they can consider in punishment, but not in guilt/innocence.