I spoke with someone who runs the gun/hunting section of a local Wal-Mart (central ohio, actually). He said that the decision to retain or eliminate firearms is being made on a case-by-case basis. He's generally unsuare if someone up in management is anti-gun, wary of the legal issues, or just keeping an eye on the bottom line. He said that some stores have phased out firearms sales, but his store was keeping theirs because they make Wal-Mart money. The other stores had weak firearms sales.
My general opinion, mostly uninformed, is that W-M thinks they can make more money using the floorspace and staff to sell things other than guns and ammo. To me that is not an anti-gun decision, per se- it is a business decision, pure and simple. That does not explain, however, why Wal-Marts out in the heart of the red states have sometimes closed their gun sections. I suspect that ultimately they want to get out of the gun biz entirely, and they've shut down the gun sections in entire regions because of this, based upon whether or not gun sales, across the entire area, were profitable enough for them.