I agree with you, that going after the pimps (employers) will do the most good, but if the wall (human, or concrete & steel) doesn't get built they'll come right back. I demand they get jail time if we deport and he comes back.
So instead of deporting 20 million people, we can just arrest, try and lock up the 5 or so million who employ them. Not hardened criminals, mind you, mostly otherwise law-abiding small business owners, the guys who sponsor Little League teams and join Rotary. Oh yeah, Americans will be completely behind that plan. /s
A book called "Reefer Madness" came out a few years ago, on the underground economy. Very worth-while reading. While I agree with building a wall and/or using the military to keep potential terrorists and other criminals out, our economy is too dependent on illegals to not have some sort of "guest worker" program. (And I agree repealing the minimum wage and every other worker-related reg might help too, but we need to be realistic.)