I genuinely don't know how to explain that the fact it requires an income of more than 21/hr to meet basic needs is all the justification that should be required.
Maybe if we stopped thinking of employees/contractors as "labor" and thought of them as people it would be easier to empathize with their needs. Do you think that your friends, family, and loved ones deserve a wage that meets their basic needs? Why shouldn't all humans deserve the same?