With a tip of the hat to Savage Minds, Andrew Galley and his philosopher friend, I direct your attention to
Muthu, Sankar. Enlightenment Against Empire. 2003.
Given the title and topic, I thought it might be of particular interest to Keith Hart and to others interested in Hart's Enlightenment-based critique of the current state of the global political economy. I just this morning purchased the book and downloaded to the Kindle reader on my iPad. A brief scan of the introduction has already yielded three interesting thoughts.
1. The "long 18th century" (late 17th to early 19th centuries) saw the flourishing of anti-Imperialist thinking among several of Europe's leading intellectuals: Adam Smith, for example, as well as Diderot, Kant, and Herder, on whom this book focuses.
2. This century was exceptional, sandwiched between centuries in which imperialism was actively embraced as a positive ideal.
3. The anti-imperialism that flourished during this period was not (Muthu's most radical claim) based on contemporary assertion of universal human rights, but rather on seeing human beings as cultural agents, whose diversity should be respected.
WARNING: I have not yet read the whole book and do not yet know how Muthu develops this argument. I only note that this claim appears to be what he is saying, based on a cursory reading of only the introduction.