The fact that some internet commerce could be intrastate does not mean that the federal government has no authority to regulate it since clearly much internet commerce is interstate and some of it is international. Again, the states do not have the ability to effectively police internet commerce, which is why gambling proponents like you keep coming up with this red herring argument.
I'm not a "gambling proponent", I'm an "original intent" proponent. I've never set foot in a casino or placed and online bet in my life. I just happen to agree with Clarence Thomas on the subject of the New Deal Commerce Clause and the "substantial effects" doctrine.
The problem is, this isn't really about interestate commerce, or even tax issues - it's about people competing with state-sponsored gambling (ala the lotteries), or gambling companies/groups that lobby hard to reduce their competition.