Walmart has never gave a crud about any complaints against them, do I doubt that they will start now. I don't think that they sell much ammo at each store individually anyways. So they may just drop ammo all the same. They only recently started selling AR type rifles, do they will be the victim of really bad timing.
If they stop selling .223 at the request of the Obama administration, I think I would have to try to live without Walmart.