How would increasing business expenses reduce the amount of taxes Wal-Mart pays?
Increasing the amount Walmart pays to it's employees, increases their business costs, thus reducing net income. Businesses pay tax on their net income, not their gross income, so the amount of taxable income would be reduced. By letting the government look after it's workers, Walmart gets to claim a much bigger profits which makes it look financially healthier on paper, but American taxpayers are subsidizing those profits with food stamps and Medicaid.
The worst of it is, that Walmart pays to poorly that it's employees don't pay income tax and are 47%. By paying $100 a week to all of it's employees, Walmart could still book large profits, their employees would pay income tax, and they would no longer be eligible for food stamps. Everybody wins. This way, the Walton Famiily wins, and the American taxpayers are screwed.