If it's not enough that Wal-Mart is a union-busting, employee-screwing detriment to communities and the environment,, or that its Chinese imports have displaced hundreds of thousands of U.S. jobs, and if it's not enough that you might run into folks like these shopping there, here's one more reason not to shop at Wal-Mart: open discrimination against gays.
As a side note, I have only been in a Wal-Mart once in the last decade. Coincidentally, this was the only time I was ever harassed for breastfeeding in public. Asa was then an infant, in a sling where she was nursing very discreetly. A greasy-haired bulk-buyer of CPC (that's Cheap Plastic Crap if you know my family's lingo) and a shopping-cart full of junk food said very loudly to my face "That's disgusting!". I would've laughed if I hadn't been so stunned. Haven't been back since.