It's because they crossed a border illegally. At which point when discovered they are entitled to exactly one habeus hearing which basically asks "Well did you actually enter illegally?" and if you did, you are returned to your country of origin (or if they won't accept you, the nearest neighbor that will).

If your country of origin wants to hold you in prison forever.. well that's not a problem the US can solve.

At no point is it because of your skin color, country of origin or your speech. It is because you chose to immigrate illegally.

That nobody else caught you or prosecuted you for 20 or 30 years is a problem, but not a defense. If you murdered someone 30 years ago, you are still guilty of murder.

And reminder, lying on immigration paperwork is also a form of illegal immigration that gets you returned home.