A commodity is something sold by price. Labor is exactly that. It doesn't matter whether the person running a machine is a PhD in Physics or a high school grad, assuming they are equally competent at the task. The determining factor for who gets the job is the price of labor, i.e. wage.
Without this understanding it is no wonder Lefties cannot grasp basic concepts.
A good or a service is something sold by price. A commodity is something that has reached the equilibrium point to where the products are so identical as to make not difference who the producer is and trades strictly on price, as quality and services are identical.
Right there, labor is not a commodity as quality and service are rarely identical. Labor is a highly differentiated market. What you are talking about is the wage paid for a particular job. Which is again, highly differentiated across markets. Consider the fast-food worker. In my city the fast-food worker will begin at minimum wage in the inner-city and minimum-wage plus 2-3 if hired in the outer suburbs. If labor were a commodity, their wage rates would be the same at all fast-food places around the nation, right?
People that don't understand the economic definition of a word shouldn't use it when discussing economic issues.