I'm pretty sure it was in Tolkien's notes.

Right, and Brin's premise is that Tolkien is a biased source.

In other words, the only way to improve the world is to become just as bad as the people currently running it? The best solution to dictatorships is to make slaves of your own, and for all eternity no less?

If those slaves were the dictators of the old era? Seems suitably karmic.

I think you're going out of your way to defend Brin's essay rather than actually using your own moral judgement.

"My own moral judgment" is a tricky thing in this situation, as it depends on which situation we're describing.

If I have first-hand experience of the events of LotR, and everything is as Tolkien describes it, then yeah, it's pretty obvious that Sauron is the bad guy.

If I have third-hand experience of the events of LotR, think that at most 90% of the description is accurate, and I think that the philosophies of the modern day are present in the LotR world, then it seems plausible that Sauron is the good guy, for the reasons Brin describes.

You might be interested in The Sword of Good, if you haven't read it. [edit] It looks like you commented there today, but I'll leave the recommendation here for any spectators to the conversation.