I think (I may be mistaken) that most Americans who immigrated here legally from Mexico (or were here before their land became part of the United States) really, really don't like people sneaking in here illegally.
I think this is more of a 'gated community'/one-world order viewpoint that opens the doors to illegal invaders. Why need borders? There is no United States -- everyone is part of the United Nations of States run by bureaucratic royals like the Bushes.
“I think (I may be mistaken) that most Americans who immigrated here legally from Mexico (or were here before their land became part of the United States) really, really don’t like people sneaking in here illegally.”
In my experience you’re mistaken. I know plenty of Mexican-Americans with close family that are illegals and none of them seem upset about it. They usually think that sneaking across the border is the only sensible thing for them to do.