I'm surprised by the complete lack of dissent or even nuance in the discussion here. I'm much more ambivalent on this: the historical record for prohibition is not good, but instagram and the like are uniquely and disastrously harmful and the companies pushing them on children are powerful in a way that has no real historical precedent. In the balance, anything the reduces the power those companies have over our lives (and our politics) has to be at least considered. In other words, I don't think this is necessarily the right measure - but I'm desperate.
Didn't regulating cigarettes kind of work?