As a Canadian visa holder here in the US, if my visa expires, I leave. If I don't, I'm in contravention of the laws and subject to deportation and exclusion from further entry. I am not displaced here - I don't belong here. I would not be persecuted, I would be legally and rightfully required to leave (and I have two US born children) - this is NOT my country and I do NOT have a right to stay here, even though I have contributed significant tax income to the coffers.

Now I understand the Mexican situation has complexities due to the complicity of the US having willingly benefited so long from the cheap, if illegal, labor and there are US born children whose needs need addressed. A compassionate resolution should be sought due to this. But the illegal alien Mexicans are neither immigrants, nor do they have any right to stay. They are citizens of Mexico and belong there. Returning them there, while an unpleasant experience, is a perfectly valid and rightful thing for the US to do.