“It” would be taxing Internet sales. As law stands, there is no sales tax on an Internet purchase you make, unless the seller has a physical presence in your state.
(Did you know you break state law each time you buy something online? You do. To my knowledge, all states have a use tax payable by the buyer up to the state’s sales tax rate, less any sales taxes paid to another state for a purchase.)
I’ve always looked at the shipping and handling as the Internet equivalent of the “cost” of sales tax; but, that is not a valid argument. The store down the road usually has higher retailing costs than the equivalent Internet retailer, even if you factor in S & H. Add the physical store’s need to add tax and you have, often, an uncompetitive situation.
And, why should one sale be tax-free and another be tax encumbered? I can’t think of a legitimate reason.