1. It's about fairness and the rule of law. The culture of this country is sliding towards conditions that foster dictatorship. Specifically, how one is treated before the law depends on one's circumstances. Whether it is Hillary getting away with blatantly illegal activity on her server or Obama unlawfully granting amnesty to millions of illegals; were on a path where consequences for illegal activity is determined by a political elite ruled by a donor class.
2. The public wants the border enforced and the politicians won't do it. The failure to control illegal immigration is indisputable evidence that our system of government has become rigged against the interests of the people as a whole. Unlike the courts ramming through gay marriage, which never won any popular votes; there is not even a fig leaf of constitutionality in this question. The Congress has the power to set immigration policy and the President the duty to enforce it.
3. It is an assault on the standard of living and even the lives of the working class. Kurt Schlichter said it best:
Amnesty was a great idea for bubble people who think illegal immigration satisfies some sort of libertarian ideal, or who only experience its impact by being able to hire a cheaper nanny. It’s a pretty great idea for the illegals too. But leave your nice neighborhood and go where a high school grad who was born here can’t get a job as a roofer since any general contractor who doesn’t hire illegals is going to go broke because his competition will. Tell somebody whose daughter is shot dead in front of him by an illegal who got arrested five times but never got deported that it’s an act of love.
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Immigration and free trade are generally good, but they impose real costs and our base is getting handed the bill. These folks have been asking us for help, and what was our response? Shut up, stupid racists.4. We have a right to expect assimilation of our culture and ideals. The current failure to enforce the border is leading to a ghettoization of Spanish speaking illegals who are not assimilating. We have lost the national will to demand assimilation of sub-cultures within our society as a prerequisite to group success. Until this changes, we have the right to call for an end even to legal immigration if we so desire, in order to ensure that new immigrants share our dedication to freedom, limited government and rule of law. Further, it is our right to restrict immigration to countries that cherish those values, so that we might preserve our own.
5. Unlimited Immigration Does Not Benefit AMERICANS as a whole. I keep having to say this. We are demanding that the government of the United States operate in a manner that benefits all Americans, not just the few who benefit from illegal competition for wages.
You may view my long history of discussing this topic. It is comprehensive.