The only principled position is that people shouldn't be treated like criminals for simply crossing a border.
The "solution" to "illegal immigration" is legalizing immigration.
A closed border patrolled by armed guards with a fence or wall (as proposed by the crazy right-wing) is something only totalitarian countries do.
A truly free nation would keep its borders open, and welcome those who would seek residency and citizenship. A free world would allow everyone the freedom to seek residency and citizenship in the country they choose, without the bureaucratic hassle of being treated as some kind of enemy trying to bring down the country.
Xenophobia, is historically, and presently, the only reason that immigration has ever been politicized. The issue attracts mostly those who want to keep "those people" out of America. Many conservatives don't even try to hide their racism when discussing the issue. They're often the first ones to racialize the issue, by talking about Mexicans and Hispanics in their usual derogatory way. Most conservatives are bigots, if most of them are proud to hate gays, is it that surprising their motives for opposing immigration would be similarly prejudiced?
Back when the immigrant rights activists held those marches, The Great American Boycott, a lot of people alleged that there were just Mexican flags they were waving. the truth was, most of those demonstrations had American flags. and LOTS of them. It looked very patriotic. This is very contrary to the idea that Mexicans desire a "Reconquista" of the Southwest. These people seemed very proud of being part of America. So much for the right-wing lies.
This is from one of the pro-immigrant rights' demonstrations. Look at all those American flags.