And here, Techdirt misses the point: Madison was talking about government-granted monopolies in the general sense, that is, one company being granted the legal right to control all production and sale of a given product, service, or raw material (e.g., a government-granted cable monopoly), as being evil things. And indeed, such monopolies, when granted by government, are evil things, because they infringe on the rights of any individual who may desire to do business in such property.
Protecting the right to control one's own intellectual property, which does not infringe on anyone's right to sell theirs or any other property, is not the same sort of monopoly. After all, we all have "monopolies" on the uses of our time and energy, for example Michael Jordon could always have withheld his preeminent basketball skills--to the detriment of us all--and been entirely within his rights. The same can be said of an author, artist, musician, etc.
Indeed, I'd guess that upon reflection, Madison would rather not have used the term "monopoly" at all with regard to intellectual property. He might rather have used the term "priviledge," which at the time meant the same as "right" today, as something that government should protect. As usual when considering what the Founders said about some issue, one must be careful to consider their use of the language and how it differs from ours.
Read the story to which Techdirt links. It's a bit different than Techdirt's version. I also concede that my reading might not be precisely the Volokh Conspiracy's, but then I'm not making entirely the same point.