As to this latest Feb. 13th offering -- I don't disagree with Madison. Something very similar was said in The Shreveport Rate Cases years later by Justice Hughes:
"It is of the essence of this (Commerce Clause - rp) power that, where it exists, it dominates. Interstate trade was not left to be destroyed or impeded by the rivalries of local government. The purpose was to make impossible the recurrence of the evils which had overwhelmed the Confederation, and to provide the necessary basis of national unity by insuring 'uniformity of regulation against conflicting and discriminating state legislation.'"
In this letter, Madison is clarifying his earlier statements about foreign trade. Keep in mind, the Commerce Clause does not define differently regulate with foreign nations and regulate among the several states. Madison is saying that although regulate with foreign nations gives our federal government the power to tax their imports to favor our country, regulate among the several states does not give our federal government the power to tax one state to favor another.
He reminds Cabel that the original intent of the Commerce Clause was to prevent injustice among the States themselves, even though the power could also be used against imports for the general good. I agree.
How do you read this letter, and what do you offer as proof?
He's saying considerably more than that. The Constitution already explicitly prohibits the federal government from taxing one state to favor another. Madison's saying that the commerce clause, as it applies to interstate commerce, was not designed to be used "for the positive purposes of the general government" - exactly the opposite of what you said at #106.