I prefer to make my gun and ammo purchases from gun and ammo people.
I won't feel the need to boycott them as I rarely choose to grace their stores anyway. Most of the things that I need that they carry I buy elsewhere already. I don't go to one big store so that I can get it all right there. When I want groceries, I go to Food City, when I want paper goods and cleaning supplies, I go to the Dollar General. When I need tools I go to a hardware store, and when I need guns and ammo, I go to the gun shop.
Now I do understand that the locations of WM stores means that for many people, WM is the most conveniently located and affordable place to purchase ammo, but I'm going to choose to look at this from a different vantage point. If WM is the closest or only place in an area to make these purchases and they cease to sell these items, perhaps this will create a viable market demand in that area for an individual to open a new gun store to provide for the gun and ammunition needs of that geographical area. It could actually be a boon for gun store owners. I'm thinking that if they do so in my area, perhaps I will apply for my FFL and just open a shop here. Just a thought.