As an opening caveat I feel I should say I subscribe to Horn Book; I frequently read YA literature and fantasy, consider myself an adult (but not a grownup - I don't feel I will ever fully reach some pinnacle wherein I will then stop growing as a person), and have considered (and am still considering) studying children's lit, possibly for an MLS.
Read Roger is the Horn Book blog. It frequently annoys me, as in the example of this post.
Now there are many many things I could say in response to this, but I believe this commenter put it the best:
Well put, Deborah. Whoever you are. You are my heroine of the day.
Edited to add: Deborah is a librarian and reviewer for Horn Book and posted her response to her own words on her lj here.
Europa Missions
3 days ago
Roger, there is a big difference between taking issue with children's literature advocates who claim that children's or young adult novels are the sublime epitome of all that is good in prose, and saying "adults whose taste in recreational reading ends with the YA novel need to grow up". You say that those of us whose recreational reading needs are met in the main by children's or young adult books are "missing a lot". Well, sure. Everyone who makes a choice is missing a lot. Those who fulfill their recreational reading needs with Barbara Kingsolver might be missing out on what John McPhee can give them. Those who will gobble up restoration comedies might be missing out on the thrill of a high-quality mystery. People who only have time to watch Grey's Anatomy miss out on Scrubs. The world is full of great ways to spend our recreational time, some marketed towards children and others marketed towards adults, some well-crafted and some less so.
You say "to say that children's literature will give a grownup all he or she needs from books suggests there is no reason to grow up in the first place". Really? My pleasures of growing up have included owning my own home, of eating Cadbury's Chocolate Spread the spoon without anybody yelling at me, having a profession and an avocation, volunteering, choosing friends, having sex, growing my own garden, making pie, and yes, reading Flora Segunda instead of cleaning my room. Was my reason for growing up really so that I would learn to appreciate Stephen R. Donaldson over Diana Wynne Jones, Jane Austen over Margaret Mahy? Because personally, I'll take having the right to vote and the intellectual capacity to vote wisely over some kind of moral requirement that my recreational reading come from books marketed towards adults.