One can look at it from another perspective -- when Walmart comes to town, typically they'll receive a tax break, which is an unfair advantage over a local grocery store. They'll also typically get a massive investment in terms of newly built infrastructure -- roads all around the lot, pipes, electricity, etc, compared to a local grocery store.
When you compare the revenue the WalMart (or any big box store) brings in compared to the amount of space it takes up (with a massive parking lot), it's typically WAY less than a small neighborhood grocery store built in the older traditional style. It's only because towns and cities have effectively subsidized these big-box stores that they've taken over. They're really a terrible deal for municipal governments in terms of economic benefits.
In many places (such as Texas), people don't consider space to be valuable because it's so plentiful -- which is true in one sense. But it's not just space we care about, it's infrastructure-supported space. Space that has roads to access it, water pipes, electricity, police and fire services, etc. will ALWAYS be scarce. These resources are expensive, and the more spread-out things are, the more money we're forced to spend on infrastructure.
This is a good way to present the issue to anyone who identifies as a free-market capitalist. Free markets require a level playing field to work properly.