Biden invited WalMart in to discuss what to ban.
WalMart is the largest retailer of guns and ammunition, which is why Biden wanted to talk to them.
Ooops - looks like it was changed to a meeting with Holder instead of Biden.
Same reason though - WalMart is the biggest seller.
If I had to guess, I'd say that the story got twisted around in the retelling, which would accont for the WallWorld manager saying what he did.