Racism!/s
1) Illegal immigrants raise the crime rate in America.
2) Illegal immigrants increase the motor vehicle accident rate in America. ( I can testify to that after a few harrowing taxi rides in Mexico with drivers who were stunningly reckless even with passengers in their cabs. A high percentage of illegal immigrants are dangerous drivers, no question about it.)
3) Illegal immigrants receive a high level of government benefits from the states and localities and divert money from schools and other priorities while driving up taxes.
4) A high percentage of illegal immigrants, if they become citizens or register to vote illegally, register as Democrats and vote for liberal politicians. These liberals can pass laws that most native-born people strongly oppose, such as the recent monstrous health care law. We have the right to resist a takeover of our country by left-wing socialist politicians because we strongly oppose the laws they vote for.
If you ask immigration advocates whether we should allow an unlimited number of Mexicans to immigrate to the US, most activists would say "yes." But if you then asked them if we should also allow an unlimited number of Chinese people to immigrate to the US, even as many as 100 million Chinese in the next ten years, I think most of the activists would say no to that idea because it would overcrowd America and overload our infrastructure. So their campaign for unlimited immigration is probably intended primarily for Mexicans and other people from Central America. We don't hate those people. We just want them to fix the problems in Mexico instead of moving up here and bringing those problems to America.