I think I'd go in with a plan. Perhaps something like:
1. Bring the books to the manager along with info about the church discipline/questionable hermenuetic concerns printed out. I've also brought up that I am aware BW is *very* popular in this area, but that I know several babies in our area who have had growth problems, been dx'd FTT or hospitalized. (Like our son was dx'd FTT. . .)
2. Acknowledge that you understand that he may not want to "censor" books with an appeal in the Christian community, but with the questionable medical information/credibility issues, he may want to consider not keeping the books on the shelves, but keeping them in the back for when parents specificly request them. When they are sold not to restock them (available through special order only.)
3. If he's not amenable to that, suggest having a flyer or warning tucked in the books. For example
this,
this or
this.
Just some ideas. . .