I know it's mostly just racism. Keep the brown people out, kick the ones who are here, and any lie in service of that is fine. But I've known enough (not many, but enough given they aren't exactly my main social circle) people over the years to know that the fear of this type of thing is real. Black people riding the bus to the exurbs to steal your TVs, Mexicans crossing the border in Tijuana to rape "your" daughters in Missouri, etc. Yes it's mostly hatred but there is fear there. I really don't understand it. Fears aren't always rational, of course, but there are so many more things to be legitimately afraid of.