Summed up in one word, sign me up as AGAINST!
Some days I shelve books that I roll my eyes at, some days I see books being checked out that I think, "why would you waste your time?" But as much as I think a major part of my job is to help students find GOOD books, and to help direct them toward literature that I believe is worthy of their time, in no way do I think the other books don't also deserve a place.
I read some books that others might find boring, or cutting edge. I allow my child to have access to some materials others would not choose, and vice versa. I've worked in libraries where we buy and shelve some really crappy books (pardon the language). I've worked in libraries where many materials were "hidden" from student access - one in particular where DK Eyewitness books on Ancient Greece were hidden away because of naked statues, such as Michelangelo's David....sigh....
I'm not a fan of the Urban Fiction genre - I don't think children need to read books about abuse, teen pregnancy and drug abuse. On the other side of the coin, I really dislike the Left Behind series of "End Times" stories for teens - another ugh.
Being in the library and looking for a book is very similar to being in the world. In both there are many choices, some are fabulous, some are mediocre, some are only silly but fun, and some are not great choices. Learning to discern good literature is a good way to begin to use discernment in other areas of life. Small choices of choosing wisely will hopefully lead to continued wise choices in bigger areas of life.