I find it difficult to think of anything that has enhanced the popularity of LotR (the book) as sad. As has been said previously, of all the millions who go to see the films, a fair proportion will go on to read the book and become fans of the Professor's works.
As for those that don't, well they would never have read the book anyway, film or no film. That's their choice (and many would say their loss). At least they have witnessed a marvellously conceived vision of Tolkien's world.
And if people who have only seen the films and not read the book profess to have a greater knowledge of LotR, or seek to assert that the films rather than the book represents the "true" story, then that, it seems to me, simply displays their ignorance and/or immaturity. If you cannot win them over with what appears to me a "no brainer" argument, then I would simply delight their efforts to make themselves look foolish.
