Many are racist extremists who believe it is their duty to change the demographics of america. They believe america owes them something just for having some ancestors who lived on the same continent 500 years ago. The immigrant community does next to nothing to reject this ridiculous and inflammatory ideology.
They are ignorant of the fact that their countries are poorer due to overpopulation and their despotic systems of government, whether socialist or militaristic. They instead blame the US for all their problems providing no evidence or citing dubious out of proportion events as evidence. There has been little attempt to show that immigrants or their home countries realise that overpopulation is a problem.
They are willing to work in extremely poor conditions and do not pay tax. As a result they usurp minimum wage worker's unions, displace America's poor and contribute nothing to the cost of social security which they leach billions from every year. Likewise their employers do not pay as much tax as they should. They believe America needs illegal workers to be as rich as it is, ignorant of the fact that the only people who benefit are them and their tax evading employers.