There's nothing stopping pedophiles from doing this now. There's nothing stopping male pedophiles who prey on young boys from doing this now or female pedophiles from preying on young girls in public bathrooms. And yet cases of such an event happening are borderline non-existent. Your entire argument is based on "what if?!" Which usually holds little concern in law making.
As for parents accompanying their children in restrooms, a responsible parent will either accompany their kids by going in the bathroom or wait outside because again, they're already susceptible from being attacked by a pedophile of the same gender or just a random crazy person.
Your argument holds no weight.