It's just the natural way of capitalism. For every one person who boycotts WalStarMartofDeath (I like this name!), there are hundreds willing to shop there to save a few cents. Even suppliers in India or China suffer from their extreme low prices. The savings Walmart gets also mean dirt pay for the factory workers in 3rd world countries who can not help but keep supplying them because if they don't, somebody else will anyway so why not, just to keep their doors open and employees paid, even if they're making pittance. Walmart's purchasing power is so immense now it makes up a big chunk of some countries' GDP. The only entity getting stronger, richer is WalStarMartofDeath. Did anyone see the interview with the CEO of Walmart recently ? Some small town protested Walmart opening there and spent hundreds of thousands of dollars in court against them for 8 years. Walmart just fights right back and will continue to do so until someone runs out of money. CEO said, it's just a small group because every time they've opened in a community that 'doesn't want them', people always flock to them when they do open. And he's right. They even dispatch special PR people to persuade reluctant communities to change their minds.
Don't buy from them if they offend you, not fish, not groceries, not anything else. Quite simple. You decide their rate of growth. I'd rather pay a little more at the mom & pop shop.