[engrpat]

"I have to pay tax, and Amazon should pay tax, it's as simple as that," he says. "There's no reason for a difference."

This guys has it wrong, he doesn't pay the tax the customers pay the tax.

[AndrewB]

You're right but there's more....

You are already required to pax your state sales tax (use tax) on any purchase you make on the internet or otherwise. It's just that only retailers with a nexus (physical location) in your state are required to collect it from you.
This will probably end soon and internet retailers will have to collect sales tax from everyone that makes a purchase from them and remit it to the state and/or municipality in which the buyer lives.
A very complex and expensive proposition.