Economists don't like protectionist unions. Who determines a "living wage"? Should someone working as a cashier in Walmart be able to afford an apartment in Manhattan?
A minimum wage just means you can't decide one day that sales are down and now everyone makes 2 cents an hour to cover costs [1]. It means there should be an implicit minimum cost to maintaining a human workforce, because people need to eat.
[1]obviously not an economist
He who pays the piper calls the tune.