I think Brad DeLong's grossly misinterpreting this Seth Stevenson (update: fixed URL) article.

Suppose that all of us who would otherwise buy coir doormats for $26.99 at Cost Plus World Market read Seth Stevenson's article in Slate, obey his injunction to become 'better than Debbie" by not buying our coir doormats--or "any other products made by Third World labor." What happens then?

Demand for coir doormats drops through the floor. Cost Plus World Market stops selling them.

... he goes on to equate this call for a boycott to just smashing the rugmakers' looms.

I guess I'm unduly answering for Stevenson here, but the point is not to drive demand for coir doormats through the floor. Why would he want that? The point is to drive demand for coir doormats made by exploiting* labour to zero. The fix by a rational company would then be to sell coir mats that meet their consumers' ethical concerns. Without legal requirements (sigh), Jack in the Box instituted a major HAACP program to cut the threat of e.coli -- because that's what their customers wanted. People want fair trade coffee and shoes from non-exploited workers and fair trade rugs -- and we can get all those things (see below for the part applicable to coir rugs.). I think Stevenson just wants everyone to have those ethical concerns when they buy.

(By the way, if Stevenson really does want to not ever buy Third World produced goods, if no ethical standard could meet his, then I apologize to the Prof.)

In comments, Eli points out that one of Brad's proposed alternatives to the boycott ("Figure out a way to generate alternatives to Mr. Shady Middleman") is already a reality.

* (and I don't mean "exploiting" in a non-prejorative technical sense)

update: Mark Kleiman gets to the core of Brad DeLong's argument:

His point is simple: however bad it is to be exploited as a third-world producer for first-world markets, not being exploited is worse.

... how is this not a false dilemma? No, seriously.