In the back of my mind I was worried that the conservatives were all going to hold the opposite of the portion Aqizzar quoted, that children do need special protection from violence and that retailers should, in effect, be surrogate parents when kids want to buy video games, by being the ones that have to tell them no. The last spate of SC rulings I read had a conservative flavor to them, and I was worried it was going to prevail in this decision. But it didn't.
The footnotes have an interesting interpretation of the idea, that The State can and does have grounding to legally empower parental judgment, just not proactively without a compelling interest to the legislature. A parent can ask a particular retailer not to sell a product to their particular child, and that retailer would be within their legal right to honor that request, because it would not constitute discrimination. But in order to forbid the sale of a product entirely, especially a purely-idea based product, the state must demonstrate a interest in doing so (at least, by the time it reaches the Supreme Court - technically unconstitutional laws and practices can stand for as long as they're not challenged).
I did find Scalia's grounding in that "compelling interest" very interesting, because he acknowledges that "corrupting morality"
is indeed a substantive legislative interest, just that in America, it has a particular definition. It is entirely permissible for the state to restrict minors' (and only minors') access to "obscenity" - specifically sexual material and foul language - because of an unscientific societal belief in the power of obscenity to corrupt a minor's mind. (Indeed, a unscientific ground that could never be disproved, because it would illegal to rigorously test to the satisfaction of the court.) And as he pointed out, essentially every legislative attempt to restrict the sale of media materials other than obscenity draws on the obscenity exception as grounding in a state interest to protect the morals of children. Scalia wants that to be a difference of kind and not degree, even as the Supreme Court acknowledges that there is not and can never be such thing as an objective definition of obscenity, but for as long as that universally accepted facet of American legislative philosophy exists, the same argument will never stop coming up.
That said, it is as he also remembers an exception that stubbornly refuses to extend outside of obscenity, and I for one see no reason that will ever change. I just thought it was amusing to hear his extemporize on. I dunno, it reminds me of the old saw that Americans are terrified of sex and totally cool with violence, while Europe is the opposite, and it occurred to me that it's an essentially ungrounded moral standard enforced in law that, precisely because it's enshrined in law, could never be challenged. Interesting to me that it turns out to be sex of all things.