1. Thomas didn't argue that the ruling "needlessly" overturned anything; he argued that the ruling misinterpreted the relevant statute and the constitution.
2. The state laws were not "aimed partly at protecting minors." They had nothing to do with minors. They were aimed at protecting domestic wineries (and distributors). The states' recent claims to the contrary in the course of this litigation are risable. There aren't a lot of 17 year olds ordering a nice cabernet over the internet.
3. Even if the laws were aimed at protecting minors, Thomas didn't argue that. It's two different ideas, spliced together:
(A) Thomas argued that the ruling needlessly overturned regulations, and (B) the regulations were aimed at protecting children.
That's cool, and well said. But as a wild-eyed libertarian I still find the regulations objectionable on many levels. Thomas is still wrong, just wrong for better reasons.