Scott Cunnigham raised an interesting question to economic historians on twitter about how one might try to estimate the effect of the Sears catalog. So far as I know, no one has yet done that, but Elizabeth Ruth Perlman and Steven Sprick Schuster may be taking a stab at it (see here).
In addition, to the quantitative significance of the catalog, I wondered what sources the story was based upon. The story seems plausible, but what evidence is it based on? Like most people, Hyman doesn’t provide references for his tweets. The video also does not state the sources for the story, and it did not appear to be included in the American Capitalism Reader that he and Baptist put together. I tweeted a reply asking him about it, but it must have been one of the thousands of responses to the thread.
Not only is the story in Hyman and Hale the same, much of the wording is the same. Both contain the quotes: "just give the letter and the money to the mail carrier and he will get the money order at the post office and mail it in the letter for you" and “these fellows could not afford to show their faces as retailers.” It seems reasonable to infer that either Hale was Hyman's primary source or they both drew from the same sources.
The first footnote is for the statements that rural storekeepers refused to sell stamps or money orders to some customers who owed on their accounts and the statement from the Sears Catalog about giving the money to your mail carrier. Thomas Clark states that : "Sometimes a customer was brought under control by the merchants refusal to order goods until he had paid his bill (page 73)." Clark was a prominent historian, but his The Southern Country Store does not provide citations. The other sources in that footnote refer to the catalog statement about giving money to the mail carrier. It is not clear, however, that Sears was trying to counter the actions of store owners rather than simply informing rural residents throughout the country that they could take advantage of rural free delivery and did not actually have to make a trip to the post office.
The other footnote cites three sources in support of the statements about rumors that Sears was black and the burning of catalogs: Stuart Ewen and Elizabeth Ewen Channels of Desire: Mass Images and the Shaping of American Consciousness published in 1982, Robert Hendrickson The Grand Emporiums: The Illustrated History of America’s Great Department Stores published in 1979, and Gordon L. Weil Sears Roebuck USA: The Great American Catalog Store and How it Grew published in 1977.
Weil also describes the opposition of small retailers and their use of racial rumors.
The bottom line of all this is that we know very little about the impact of Sears in the South or other rural areas, and consequently we no little about its ability to undermine some of the results of Jim Crow. It is quite plausible that Sears provided large benefits like those suggested by Hyman, but we don’t know. It is possible that store owners spread rumors about race, but we have only Roebuck's recollection to that effect. It is possible that they organized catalog burnings, but we do not know. It is possible that some of Sears actions were attempts to counter racism, but we don’t know.