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.
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.
Is a book character being gay unsafe for kids in a way that the same character being straight is not?
If a pre-teen can understand the concept of sex, what’s so difficult about explaining that _some_ people have non-mainstream sexual attraction?
A better example is restricting access to actually dangerous ideas, like “Mein Kampf”.
But yeah, I don't want to be expressly forbidding disagreeable content to my kids, I want them to learn to choose content that is worthwhile themselves.
They cannot and do not understand that concept which is why exposing them to it is a serious criminal offence.
Whether or not they should learn that as a pre-teen is certainly up for debate, and many people / cultures have different opinions on that.
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.