>You're approaching this story with the a priori conclusion that any gendered social behavior is bad.
No, I'm saying that the enforcement of the social norm on the child is wrong. Social norms are enforced through punishment, though the punishment is often very light (such as being the butt of a joke or even just being asked to justify one's behavior, but these are separate treatment than those who conform receive). At worse levels it can lead to ostracizing and bullying.
>If you're trying to convince me that boys are harmed by the fact that we don't advertise high heels and Barbies to them you're going to need to back this up with strong evidence.
You seem to be reading this backwards. It isn't the lack of advertisement, it is that the existing advertisement feeds into norms which are then enforced against those who don't meet those norms.
>You're also assuming that a significant number of boys want to use such things but the advertising prevents that.
I am assuming no such thing. There needs to only be a single individual harmed by the social expectations fed by the advertisement for it to be harmful.
>I recall a couple studies in which children were raised from birth or early childhood in gender neutral environments, but the kids displayed gendered preferences and behavior much like the rest of society.
Yes, kids do tend to have gendered preferences in what toys they play with. That you bring up something unrelated to my point makes me think there has been some misunderstanding of what I'm trying to say. So let us give a different example and skip gender since that seems to lead to a lot of incorrect assumptions being made about what I'm saying.
Go with an advertisement campaign that shows kids who play with a specific brand of soccer ball as being better than those who don't, either because of lack of access or lack of interest. If the marketing is aggressive enough, which isn't hard when dealing with young children, it can lead to children discriminating and engaging in social punishments against those who do not have the status symbol.
While the exact advertising leading to it is far more complex than a single commercial, this is a real life problem with brand name clothing and displays of wealth among school age children (especially preteens and teens). Children who cannot afford the brand named goods to display to peers are treated negatively compared to those who do, which is a harm created by the advertisement. It can lead to some extreme cases of discrimination depending upon how strong the message sent to children is. The classical example being the teacher who told students of different eye colors that some were naturally better than others, a message that is often largely mimicked in advertisement with purchase of the brand swapped for eye color.
>A very probable explanation is that these behaviors occurred on their own
I've never known any animal other than human have a preference for Nike over New Balance.