Lucky enough for us that the Von Mises website reprinted this beautiful essay from Von Mises (oh, if it were only untainted by the regulators):

"Our economic system — the market economy or capitalism — is a system of consumers' supremacy. The customer is sovereign; he is, says a popular slogan, "always right." Businessmen are under the necessity of turning out what the consumers ask for and they must sell their wares at prices which the consumers can afford and are prepared to pay. A business operation is a manifest failure if the proceeds from the sales do not reimburse the businessman for all he has expended in producing the article. Thus the consumers in buying at a definite price determine also the height of the wages that are paid to all those engaged in the industries."

I submit that many, if not most, historians are lousy historians as well.

What further proof is needed?

David,
I cited the editorial, because it is proof that the same motives that Don mentioned were being questioned at the time of the passage of the act. Unfortunately, I cannot read minds, so Sherman’s true motives remain closed to us. However, I think historians spend a lot of time trying to figure out the motives of historical figures, and (considering that tariffs limit competition, while trust busting supposedly enables it) I find Don’s and DiLorenzo’s conclusions very plausible. As for the validity of the Sherman Act, well the amount of scholarship on Anti-Trust suggest that the whole field is a waste of time and that the Sherman Act and its even more evil sister (the Clayton Act) have done immeasurable harm to consumers. Wikipedia has a great quote from Alan Greenspan on the Sherman Act.
"No one will ever know what new products, processes, machines, and cost-saving mergers failed to come into existence, killed by the Sherman Act before they were born. No one can ever compute the price that all of us have paid for that Act which, by inducing less effective use of capital, has kept our standard of living lower than would otherwise have been possible."

October 1890: Sen. Sherman champions a tariff hike that more thoroughly shields domestic producers from foreign competition, enabling domestic producers to charge prices higher than they would otherwise be able to charge.

It's not proof, granted; but it's a quite-plausible conclusion from these facts that Sen. Sherman's motives for putting his name on the Sherman Antitrust Act had very little to do with protection consumers from monopoly power.

Opponents of the tariff act like the NY Times attacked Sherman in an editorial. So what? Questioning the motives of others may be an effective technique, but it should never be confused with providing proof. Would you rely upon NY Times' editorials to give you the straight scoop on other subjects? Even if Sherman acted with base motives, that says nothing about the value or validity of the Antitrust Act itself.

The article is dated 1890, not 1980.

http://query.nytimes.com/mem/archive-free/pdf?_r=2&res=9B06E4D7103BE533A25752C0A9669D94619ED7CF&oref=slogin&oref=slogin

“That so-called Anti-Trust law was passed to deceive the people and to clear the way for the enactment of this Pro-Trust law relating to the tariff. It was a humbug and a sham.”
There are more gems in the article.

Some may take DiLorenzo seriously as an economist, but he's an embarassment as a historian. Ditto for Libert's speculations about Sherman. Innuendo is not the same as proof. Considering that the act passed both houses of Congress with overwhelming support, it becomes very hard to see it as a vehicle for one man's political revenge upon another. Regarding your imputation to Sherman of using the bill for "political cover", what evidence exists to support your speculation? Sherman had a successful political career which spanned decades. Why would he want or even need political cover given his secure position?