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.