Above the Law & Common Sense
There are two issues:
1: Anyone can setup an account & lie about their age. This is perpetuated by idiotic parents who permit their children to do this. There simply has to be some sort of legally binding age verification that ties the user to an account. This is next to impossible if parents then setup account for minors. We are then back to iris or fingerprint verification. Responsible parents and children will sort this out. The majority will not. This single biggest concern is that as I understand it, the default makes the profile visible.
2: Facebook in particular does not give a stuff about consent, or decency. If they did they would take down vast amounts of posts and images long before they were published. They simply do not care, prinicapally because sick people will then try to find these posts. increasing Facebook's revenues. There will never be enough people offended enough to close their accounts to make even the slightest dent in usage. Companies are very unlikely to remove advertising because overall, it is probably not enough for them to worry about.
Facebook and Zuckberg can do what ever they like & unless they go so extreme as to cause a problem to a global company or the American politcal system, nothing will change. It is in MZ's words "Free speech".
Unfortunately the term "Free speech" is now used to justifiy huge amounts of frankly questionable decision on leaking information or posting inappropriate pictures.
I wonder what the public reaction would have been the instant video/pictures/post woudl have been if graphic images from the following had been posted, not what just reached the newspapers:
Lady Dianna Spencer's ill fated crash in Paris
Body parts of Americans from the World Trade Centre
Bloody Sunday in Norther Ireland
Concorde Crash in France
MP Airey Neave blowin up by the IRA in London
Regents Park bandstand bomb.
The sad thing is that I suspect there would be a howl of outrage and increased traffic as it appears that developed Western culture now expects this a form entertainment. Facebook and the like are only delivering what the majority of the so called "developed world" wants. With the global reach using the Internet, policing this content is simply impossible as there is no single body with any power to enforce it. There is so much money sloshing about that the fines that may be levied are just operating overheads.