When the Walton's employ people for less 40 hours a week just so they don't have to pay benefits, they are externalizing that cost to the other taxpayers (food stamps, housing assistance, health insurance).
I'm not without blame here. I'm pretty sure whenever I eat at a Chinese restaurant that they are exploiting workers. The fact that the workers are better off than they would be in China isn't really a defense.
It isn't just my standard of living either. go to walmart at 11pm, or 2am and see the shoppers there. their money goes a lot farther at walmart than it does at costco. The massive scale of walmart's business coupled with the billions it spend on trans log drives prices down. If walmart weren't there, how much higher would target's prices be? or the prices at dollar general?
aren't the living costs of walmart employee's even subsidized by tax payers? i believe i saw articles about this.
(edit): http://www.huffingtonpost.com/2013/05/31/walmart-taxpayers-h...
They can get away with it because they're gigantic. And that's the problem with wealth inequality; extreme wealth isn't a problem per se, but it involves a concentration of power that allows the extremely wealthy to switch over from enriching themselves by making everybody better off to enriching themselves by hurting others.