Children who are 9 months old have been exposed to 9 months of gender indoctrination. Human brains are nothing if not completely plastic, always responding to whatever they are exposed to. And, humans are inclined to feel comfortable in categories. Since children don't have Republican or tennis player to pick from, they assiduously soak up what is coded for their gender instead.

And even if most boys would naturally select "boy toys", I have no problem with that. Whoever they naturally are is fine - but the fact remains, that's not how it works in reality. Boys and men police and bully each other into maintaining Man Box traits and behaviors which causes 20% of those who don't fit comfortably in that box to try to kill themselves. Why on earth is that OK to anyone?

I was told my whole life about what was allowed and appropriate for me because I was a girl/woman and a lot of that was incredibly restrictive and damaging to my self-esteem and confidence. Shoving people into gender boxes is harmful all around, particularly when it's used to marginalize and disempower them.

I haven't said that there is no fundamental aspect to gender -although I don't think it's what gender essentialists think it is. I don't doubt trans people who know, despite what their bodies say, that who they are is not a fit for that. But at the same time, there are nearly infinite ways to be a man or to be a woman (or to be non-binary or intersex) and they should all be acceptable. As I've said in other places, I'm really, really clear that I am a woman, but I don't want anyone telling me how to act or think, and I sure don't want them making assumptions about me simply based on that fact alone. Do you want people making assumptions about you (or your kids) based solely on your gender?