Sowell is right here. Take your analysis a few steps beyond where you stopped.
That we need to eliminate minimum wage? Sure. But it won't happen. Would we be stronger economically if we could dramatically cut down the number of illegals? Not if we didn't eliminate the minimum wage and various other social benefits that create disincentives for taking low paying work.
Is it an "insult" to decide to offer foreign worker status to a large portion of the illegals currently here (because that would sanction law breaking)? No more than it was to end Prohibition back in the 30s when millions of Americans became lawbreakers.
Is Sowell right about having stronger border enforcement? Yes, to a point. But he maybe ought to go back and re-read his own book, Knowledge and Decisions.