A little of it's fair use, a little of it's that after the Scans_Daily TOSing on Livejournal, even our most passionate supporters noted that it sometimes could be an uncomfortable place to be when the personal insults started being tossed around.
Add to that the fact that the initial confrontation with the creator that triggered the TOSing was over a personal insult. I personally think it's sensible to try and guide people to talking about the books, not the people behind them as A) it hopefully makes the community a little more creator friendly and I think most of us enjoy talking to creators if they're interested in discussing their works and B) makes a repeat of the circumstances of the last TOSing hopefully a little less likely.
99% percent of the time when someone said "What the fuck, creator, you stupid asshole" it was about something in a book anyway, so might as well just talk about the book in the first place. And you can't hurt a book's feelings by saying how goddam shit it is.
That's my view anyway.
Of course, that's just the creators part. The fact is, members should also feel comfortable here and be able to get into heated debate without one person threatening to stab another in the face, or similar.