Why do people treat Mexicans like they are lower than dirt?

Now, now yur being to politically correct when you said "we're all equal" because, I mean, they aren't used to a strict place like America yet, with all the seemingly snoopy government guys and police. The manager must only be tense, because the government suspected the Arizona wildfire to be started by illegal immigrants. And the government and cops have really ben gun-hill about immigrants and border patrol, since the death of you-know-who.