That's a valid opinion. Here's a different one: the ethical thing to do would be to repatriate Mexican citizens to Mexico, thereby demonstrating that we have a zero-tolerance policy for cutting the line and breaking our laws. It will cost more and take considerably more effort, but upholding our laws is the ethically correct thing to do. Time spent here does not constitute legal status. The only point of contention I can think of is what should be done with anchor babies.