another way to justify it is that it will pay for itself by saving us money on detention facilities, health care, court proceedings, education, law enforcement, English classes, and all the other costs (financial and otherwise) that the illegals bring upon us
OK, but you're also going to have to truthfully state that the economic benefits of having a large pool of low-cost labor available will end.
The question is what kind of costs are being imposed. If the costs you cited are avoided, but only at the cost of (1) a border security program of nearly equal expense and (2) forgoing the benefits of low-cost labor, then you're going to have one hell of a fight to justify it.