As @mmasnick points out, so-called "age verification" laws to participate in online activities amount to creating a license to read, and to speak. Anonymity would effectively be banned.
It's also a license for other people to know, in a granular way, what you are reading and saying -- and your personal information would be held by people who cannot be trusted in any way.
Maybe the worst part of this is that some alleged liberals are all in for this evil plan.