Andrea Harris, whose blog I read daily, has an interesting discussion of this exercise in missing the point by David Brin. Andrea has already done a thorough job of taking the argument apart piece by piece. I just wanted to add something about the "nostalgia" in LotR.
There is indeed something "backward looking" about LotR, but it's not anti-technology (what are the Elven Rings, after all, but good technology that allows for Lorien and Rivendell?) or wholly pro-monarchy. It is rather a completely and characteristically human longing for the good things in the past (I mean here the personal past), projected by Tolkien into a deep, bittersweet sadness about inevitable loss. You might say it's what someone would feel in 1918 looking back at the summers of 1913 or 1914 (but that's another posting).
I have an amazing two-year-old daughter, and I love watching her grow up, but every once in a while you get an incredible pang of sadness at what will never happen again: she'll never fall asleep on my chest like she did when she was a tiny baby; she'll never wear certain things again, or like certain toys. The past is gone forever. Tolkien's genius was to capture that emotion and give it a shape and form, so that Frodo at the Grey Havens is immediately understandable to readers in a deeply personal way. People, like Brin, who want to claim that this feeling is politically retrograde or base or wrong are simply missing out on a great deal of human emotion. We don't have to live in the past, and in the character of Denethor Tolkien shows how destructive such living could be. But it is not merely acceptable but actually good to remember, long for, and even grieve for those things that were great and beautiful but which are now, as a price paid for our free will and open future, gone forever.