I think that is the real issue. We homeschool so of course we are very involved with our kids in every facet of life. We talk about and verify everything before our children read or see it. Unfortunately that's not true for many families, but as you said, we cannot hold literature responsible for bad parenting.
Parenting the right way is a job that requires a lot of work. Since kids are our legacy we do what we think is best, no matter how much work it is or how inconvenient that makes our lives. For us we don't really see any difference between Harry Potter and the 1971 movie Bedknobs and Broomsticks.
We try to be open to instruction in all ways. That is, we try to remain teachable in case we're wrong somewhere. But... If there are valid arguments against letting children watch Harry Potter than I haven't yet seen them.
I fell in love with The Hobbit when I was ten, because it was so completely different from what the other kids were reading, and I was seeking out stuff that would continue my love of Baum and Dahl. I wanted fantasy, and found it in the Hobbit. Bilbo became my favorite character (still is to this day) and was desirous of sending a fan letter to Tolkien, but found out from the librarian that he had passed away three years prior to my discovering the book. Then she said those magic words : "he wrote even more about hobbits..." and LOTR became a whole new world to me.
I do agree with those who have said they couldn't stomach Tolkien's writing - to a point. Anytime he wrote through the eyes of the hobbits, I was enthralled. It was when he deviated into the "language of the Men" or Elves that I found my attention slipping into disgust or boredom.
I realized a brilliant thing about Tolkien's book though not too long ago. One can tell which hobbit is "telling the story", and the POV is very much line with the personality of the hobbit. Merry's POV is very businesslike and extremely formal, almost sounding like he is writing the medieval textbooks or Biblical passages. Sam is very down to earth and pragmatic. Frodo does exactly what happens to him as the story progresses : disappears and subverts himself to reaction, which just highlights the fact that his every step closer to Mordor erases more of his original personality. Pippin is my favorite, because his POV is very similar to Bilbo's and can tell a good story, with a few smart remarks thrown in for good humor.
That's what I love about Tolkien, and I find it rare that a fantasy writer can do the same.
I love Ursula LeGuin's writing for the exact opposite reason I like Tolkien though : she is very precise and elegant in her choice of words. She doesnt use a whole lot of description, but what she does say speaks volumes.
And then, there is Patrick O'Brian....
I would never say that JKR's Potter books were in the same league as those authors, but there are some merits to what she has done.