I don't have a solid stand on the issue, but it annoys me when people argue in support of illegals with "This country was built on imigrants!". Just because they're all called "imigrants" doesn't make them the same people, it's a vague generalization. There's a difference between legal european christian imigrants who came to found the country, and illegal south american imigrants looking to mooch off the system. I'm by no means painting this picture to apply it to all people of any group of course, I'm just sayin' it's a stupid comparrison using vague reasoning.
It's kinda like people who attack christians by saying "well christians did such_and_such an atrocity!". Doesn't make you vicariously guilty by religious association. And likewise, mexican illegals shouldn't get credit by mere linguistic and situational association.