I've rejected accepting the assertion that it is without any evidence to back it up. I have evidence that it isn't.
From Joseph Story's Commentaries on the Constitution
§ 1075. The reasoning, by which the doctrine is maintained, that the power to regulate commerce cannot be constitutionally applied, as a means, directly to encourage domestic manufactures, has been in part already adverted to in considering the extent of the power to lay taxes. It is proper, however, to present it entire in its present connexion. It is to the following effect.--The constitution is one of limited and enumerated powers; and none of them can be rightfully exercised beyond the scope of the objects, specified in those powers. It is not disputed, that, when the power is given, all the appropriate means to carry it into effect are included. Neither is it disputed, that the laying of duties is, or may be an appropriate means of regulating commerce. But the question is a very different one, whether, under pretence of an exercise of the power to regulate commerce, congress may in fact impose duties for objects wholly distinct from commerce. The question comes to this, whether a power, exclusively for the regulation of commerce, is a power for the regulation of manufactures? The statement of such a question would seem to involve its own answer. Can a power, granted for one purpose, be transferred to another? If it can, where is the limitation in the constitution? Are not commerce and manufactures as distinct, as commerce and agriculture? If they are, how can a power to regulate one arise from a power to regulate the other? It is true, that commerce and manufactures are, or may be, intimately connected with each other. A regulation of one may injuriously or beneficially affect the other. But that is not the point in controversy. It is, whether congress has a right to regulate that, which is not committed to it, under a power, which is committed to it, simply because there is, or may be an intimate connexion between the powers. If this were admitted, the enumeration of the powers of congress would be wholly unnecessary and nugatory. Agriculture, colonies, capital, machinery, the wages of labour, the profits of stock, the rents of land, the punctual performance of contracts, and the diffusion of knowledge would all be within the scope of the power; for all of them bear an intimate relation to commerce. The result would be, that the powers of congress would embrace the widest extent of legislative functions, to the utter demolition of all constitutional boundaries between the state and national governments. When duties are laid, not for purposes of revenue, but of retaliation and restriction, to countervail foreign restrictions, they are strictly within the scope of the power, as a regulation of commerce. But when laid to encourage manufactures, they have nothing to do with it. The power to regulate manufactures is no more confided to congress, than the power to interfere with the systems of education, the poor laws, or the road laws of the states. It is notorious, that, in the convention, an attempt was made to introduce into the constitution a power to encourage manufactures; but it was withheld. Instead of granting the power to congress, permission was given to the states to impose duties, with the consent of that body, to encourage their own manufactures; and thus, in the true spirit of justice, imposing the burthen on those, who were to be benefited. It is true, that congress may, incidentally, when laying duties for revenue, consult the other interests of the country. They may so arrange the details, as indirectly to aid manufactures. And this is the whole extent, to which congress has ever gone until the tariffs, which have given rise to the present controversy. The former precedents of congress are not, even if admitted to be authoritative, applicable to the question now presented.
I read through the entirety of what you posted. What it defends is ‘state imposts and excises’.
What it does not defend is your thesis that the federal government cannot regulate imposts and excises.
Still waiting for some language from the constitution which says this, btw. I’ve been quoting the consitution all the time, and amazingly enough, you still haven’t cottoned on. :)