For them, my analogy is spot on. In the 30s they'd have been yelling about the kind of precedent it would set to make alcohol legal again.
Oh good grief! Your analogy to Prohibition is a joke! You still don't grasp the issue, do you "professor"...? They resolved the issue/dilemma of Prohibition in the '30's not by deciding not to punish all the people who had been consuming alcohol but, realizing that laws against the consumption and sale of alcohol were just not practical (and actually counterproductive), they suspended all the national anti-alcohol statutes altogether. They simply allowed everyone to go back to drinking drinking alcoholic beverages.
So, if we were to actually handle the illegal immigration dilemma in the same way that they handled the problems with Prohibition in the 1930's, we would basically suspend the laws against illegal entry by immigrants into our country and allow virtually anyone and everyone throughout the world who wanted to come here to do so ( open boders ).
I really don't think that is what even you actually want and that is why your analogy ( obviously ) fails.
Now don't get all huffy. You do realize, don't you, that there was a time not so terribly long ago, when anyone could immigrate to this country? Then we placed significant restrictions on immigration. Today, mostly because of economic demand, we find those immigration laws being violated on a massive scale. The idea that we can make this problem go away by simply "enforcing the law" is exactly like claiming we could have stopped illegal drinking the same way. Note that I'm not saying we should do away with all immigration laws. I'm just saying that in contrast to Sowell's point, we are not obligated to deport all illegals nor to refrain from changing the law.