The issue is that by forcing children to identify themselves to access information, be it the internet or a library, etc is that by doing so you are normalising that there are limits to what knowledge a person is allowed to consume or possess based on who they are.

That immediately paves the way for expansion of those restrictions.

We see that currently with efforts to "protect the children" by limiting access to things like porn. It's reasonable on it's face but immediately gets weaponised to start banning access to any content that isn't gender or sex normative.

Indeed. This is how precedents get abused.

There is a very intentional framing of "protecting children" while book bans are really targeting what are more fairly described as "young adults". The goal is of course ensuring young adults are only exposed to a certain world view.

It is good to normalise that because that is true. Children are not allowed access to lots of things, and that is a good thing.

Yes, "content that isn't gender or sex normative" should be included. Children should not be exposed to sexual subcultures or encouraged to experiment with gender non-conformity. They are not ready to handle that.