alt Hacker NewsFirst, children also have a right to free speech. It is perhaps even more important than for adults, as children are not empowered to do anything but speak.
Second, it's turn-key authoritarianism. E.g. "show me the IDs of everyone who has talked about being gay" or "show me a list of the 10,000 people who are part of <community> that's embarrassing me politically" or "which of my enemies like to watch embarrassing pornography?".
Even if you honestly do delete the data you collect today, it's trivial to flip a switch tomorrow and start keeping everything forever. Training people to accept "papers, please" with this excuse is just boiling the frog. Further, even if you never actually do keep these records long term, the simple fact that you are collecting them has a chilling effect because people understand that the risk is there and they know they are being watched.
> First, children also have a right to free speech.
Maybe I'm wrong (not reading all the regulations that are coming up) but the scope of these regulations is not to ban speech but rather to prevent people under a certain age to access a narrow subset of the websites that exist on the web. That to me looks like a significant difference.
As for your other two points, I can't really argue against those because they are obviously valid but also very hypothetical and so in that context sure, everything is possible I suppose.
That said something has to be done at some point because it's obvious that these platforms are having profound impact on society as a whole. And I don't care about the kids, I'm talking in general.