I think one of the most profound truths about immigration is that no one chooses where they are born. The vast majority of people in America are the descendents of people who came here from somewhere else, many through official channels, many not. The fact is that if we choose to vilify today's immigrants then we are vilifying many of our own ancestors. Most of our ancestors have a great deal in common with today's immigrants, or at least the immigrants that are being targeted at the moment-- they were/are all mostly non-english speaking, poor and uneducated and were/are in search of a better, safer life.
I'm not denying that immigration today has problems, but I am rejecting the notion that today's immigrants, specifically from Mexico and Latin America, are any less deserving of a chance than anyone else's parents, grandparents, great-grandparents and so on. Let's not forgot in our zeal to protect ourselves that one of the characteristics that sets America apart from the rest of the world is that we are a nation established and built by immigrants. We are turning our backs on ourselves, our history, if we declare immigrants to be a "threat."
So whenever someone says something ignorant or ugly about Those People they're talking about all of us, in one way or another.