I don't always have a lot of time to make long comments.
But I do not believe that those people learned racism from US.
But the reason that young Mexican-Americans claim to want to take back "their" land is not because they are racist, but because they were TAUGHT what they are saying, not by their uneducated (and probably illegal) parents but by their American teachers and American media. That d-ckhead in Colorado nwhose diatribe got recorded is one example.
In a sense I can't blame them for being so angry and holding up those placards. To them, it's just what they've taken for granted for so long. And now, when Americans want to reclaim the culture, the history, and the border, the radicalized Mexican-Americans think they are being deprived of what is theirs.
The analog is an easement on property. Suppose that you have a huge property lot; and that passing over your lot shortens distances by people walking from one end of town to another. Well, technically they're tresspassing but you ignore the problem for 20 years because it's really not doing any harm. But if you decide to crack down, then the users of those paths on your property will put up a hue and cry over being denied access, even though it's your property, even though they were technically tresspassing. [The law is on their side too, by the way.]
America has given illegal Mexicans an easement on prosperity for the past 35 years. Free education, free healthcare, free welfare and housing assistance, nominal enforcement of immigration laws, plus an education that tells them they're only taking back what was rightfully theirs. They didn't bring it from home. They got it from here.
As much as I want to send them all home, in a sense I don't blame them for complaining.