You teach them the harm of smoking and online grooming. You teach them to not accept cigarettes or sexual advances from others. And you build a trusting relationship with them so in the unfortunate case they do mess up, they trust you enough that they tell you what's going on, instead of hiding abuse they suffered from others so their parents don't berate them for going unsupervised online.

Idealistic, I know, I know. But so is the idea that you can seal your kids in an airtight bubble and never risk any harm without the harm avoidance becoming harmful in itself. Or that the lawmakers in this country and elsewhere actually care about child safety at all, when they will not move a finger to prosecute those who hanged out with Epstein on his island.