Not long after [Andrew Ferguson] and I met, we were driving down Pennsylvania Avenue and encountered some or another noisy pinko demonstration. "How come," I asked Andy, "whenever something upsets the Left, you see immediate marches and parades and rallies with signs already printed and rhyming slogans already composed, whereas whenever something upsets the Right, you see two members of the Young Americans for Freedom waving a six-inch American flag?" "We have jobs," said Andy. [P. J. O'Rourke, from the introduction to Parliament of Whores]
The other reason is that, in theory, immigration enforcement is already the law. I wrote in 2008 that
the millions of Americans who support enforcement mostly don't feel they need to march in the streets to support the law. This is a phenomenon that compares to the rarity of pro-Vietnam War demonstrations in the Sixties and Seventies, and the extremely rare "Peace Through Strength" counterdemonstrators during the pro-Communist "Nuclear Freeze" movement in the Eighties.
In both cases the general public didn't feel the need to march, since the national government was on their side. When some network news people referred to "Peace Through Strength" demonstrators in the Eighties as members of a "fringe", conservatives pointed out that the idea of deterrence was not only the official policy of the US Government, (supported by the American people and a strong bipartisan consensus) it was the policy of of every other government in the world. It was the pacifists who were the fringe, not matter how many people they could pack into Central Park for a nuclear freeze rally..
In the same way, immigration enforcement is already the law, and...wait for it...the policy of of every other government in the world. Especially the government of Mexico. But we do need to march—if we don't, we'll no longer be able to say "We have jobs."