That doesn't make any sense. If you want "cheap labor [that] can't complain about mistreatment," you want a weak border, not a strong one, because a weak border creates a larger pool of illegal immigrants to draw from.
A strong border, at a minimum, reduces the supply of illegal immigrants, and may even push the employer into hiring people with legal immigration status who can complain and sue over mistreatment.
> It helps that a decent portion of the population hates and/or is fearful anyone different from themselves. That is what's allowed for these even more draconian and brutal measures.
I'd put it another way: a large part of the population has been put under a lot of stress and pressure, while simultaneously being intensely conditioned to not blame the people actually responsible. That stress has to go somewhere. Don't blame the little guys, even if you find them contemptible because they're not from your culture. Blaming the little guy (for "hat[ing]...anyone different from themselves") is another aspect of the conditioning that protects those actually responsible.