Why is it hilarious? It's hard to argue that net neutrality isn't about commerce, because most of the common talking points in favor of it explicitly refer to commercial activity ("paid lanes", etc.).
While I dislike the implications of this argument for net neutrality, legally, it's actually a pretty solid argument. The Supreme Court has already ruled - many, many, many times - that states have very little power to restrict interstate commerce. These cases all happened around the turn of the last century, so the precedents are pretty well-established. And the ability of the federal government to regulate interstate commerce is an enumerated power, so there's pretty much no way to deny it.
Conversely, the Supreme Court has also expanded the scope of the Commerce Clause so far over the course of the 20th century that it's basically given the federal government the authority to regulate absolutely anything that happens in the states, because anything has the potential to impact interstate commerce.
To give you an idea of how new this idea is: at the time Prohibition [of alcohol] was enacted in 1919, it was a Constitutional amendment enforced via the prohibition of "manufacture, sale, or transportation" rather than posession, because it was believed that the federal government did not have the power to outlaw possession of a substance. Similarly, the original ban on marijuana wasn't even a ban at all - it was a cleverly-worded tax act which made it illegal to possess marijuana that hadn't been taxed, but also made it impossible to prove that you'd paid the tax.