The article is based on the assumption that when we ban things for children only, it is because we perceive them to be harmful to children only. I don't think that is true. Nobody thinks adults are immune from the negative effects of cigarettes or alcohol. But adults are, in general, allowed to harm themselves. Children are not, because there is an acceptance that children are less able to make informed decisions. You can take issue with that and obviously bright-line rules based on age are highly imperfect, but it's a very different discussion to the one the article is trying to have.
Granted, there is also evidence that social media has particularly harmful effects on children, which no doubt strengthens the argument. But in the general case bans targeted towards children are not (just) about that.
Ultimately the article seems to be trying to argue (implicitly) that we shouldn't ban, regulate or tax anything, because if we were to do that, we would then need to ban, regulate and tax everything in order to be "consistent". It's a common argument I see from libertarians online, including on HN. If you're going to ban guns, surely you should also ban knives and cars? If presented with a choice between permitting one specific thing or prohibiting all the things, most people will choose the former. But it's a false dichotomy. The law can treat different things and situations differently, even if those things/situations have some commonalities.
Cigarettes and alcohol are more strictly regulated for children than for adults, but are regulated for both, because adults are allowed to harm themselves, but there is a general agreement that the law should discourage that. Yet the call for a social media ban on children is (or at least that's my impression) never accompanied with proposed regulation for adults, or a stricter enforcement of already in place but unenforced rules. I totally agree with you on how the "we shouldn't ban A, because then we should ban everything else" is a false argument, although it didn't seem to me that was the argument on the article (but close to everyone on HN catched that, so I'm going to read the article again with a fresh mind in a couple of days, maybe I just missed that)
But also, the effects of some things on developing children are different (arguably more impactful) than on adults.
We talk about education, nurturing, etc, and how vital they are to children. We also know drugs that have different effects on children than on adults.
Why then it's so surprising social platforms could also have a bigger impact on children?
Granted, there is also evidence that social media has particularly harmful effects on children, which no doubt strengthens the argument. But in the general case bans targeted towards children are not (just) about that.
Ultimately the article seems to be trying to argue (implicitly) that we shouldn't ban, regulate or tax anything, because if we were to do that, we would then need to ban, regulate and tax everything in order to be "consistent". It's a common argument I see from libertarians online, including on HN. If you're going to ban guns, surely you should also ban knives and cars? If presented with a choice between permitting one specific thing or prohibiting all the things, most people will choose the former. But it's a false dichotomy. The law can treat different things and situations differently, even if those things/situations have some commonalities.