We allow the second system to exist because it is meant to play some very small part in our shared social vision, and it is meant to pay for its associated cost

We allow the second system to exist because it is meant to play some very small part in our shared social vision, and it is meant to pay for its associated costs. If it wasn't designed to bear the cost of paying its workers a wage that we collectively deem to be decent, then perhaps it was poorly designed and deserves to be reevaluated. I think that judgement belongs to all of us. And if we consider all of the locally owned retailers that have gone out of business due to Walmart's (admittedly efficient) business practices, then saying something like "Walmart doesn't need to exist" really isn't that all that crazy.