Here's where you skipped the part of my prior post that already answers this. I'll quote myself then elaborate. "This fear.... is no differeent than the xenophobic, bigoted fear we've seen of Catholics, the Irish, Africans, Southern Europeans, Jews, Eastern Europeans, the Chinese, etc... in the 1850s, the 1880s, the 1900s, the 1920, etc..."
So, today, its the "Europeans" against the Hispanics. Well, in 1890, it was the WASPs vs. the Southern Europeans. They were the ones who wouldn't integrate and who were going to "destroy" this country. In the 18540s it was the English Protestants against all those scumbag Irish Catholics who were going to ruin the country (hello "Know Nothing" party) In California in the 1880s, its was the Irish vs. the evil Chinese. In the 1920s it was Western Europeans protecting American values from the hordes of Eastern Europeans and Jews, etc...