Mexican illegals have served the purpose of driving down wages and labour rights, so from the perspective of the American working class, their disdain of illegals is perfectly justified, even if misguided (since the true culprits are the people in charge of the institutions that keep letting them in, and using them in place of native workers).
The American capitalist elite love their illegals, and would love nothing more than to continue bringing in cheap, desperate labour with lesser civil rights.
It is the common man, the working class person, the average American citizen, who must once again put an end to the exploitative methods of the rich, as he has done so many times before, in American history, through slavery, through indentured servitude, each time prompting an outcry from those that benefited from such practises.