If big corporations have to pay workers living wage they can't keep prices of goods and services artificially low at the expense of workforce. That automatically makes small business owners competitive.

Or in other words if they want to beat price and value of $19 pizza pie made by Tony they would have to lower their corporate profits or offer better product and expedience than Tony. Rather than simply driving Tony out of business by offering $5.99 pizza and than jacking up the price when Tony goes belly up.

Same goes for a local pharmacy, grocery store, hardware store, doctors office or any other business you can think off.