Just because previous generations of Americans fell for a Ponzi scheme named Social Security does not mean we need to let millions of illegals into the country just so they can pay for the baby boomers retirement. We are a nation of laws or we are not. If the government can pick which laws to obey maybe I can to. Maybe I will just stop paying taxes. The government would come after me big time. There would be consequences for me why not illegals.
That "there must be consequences" (for being here illegally) DOES NOT EQUAL "expell them all." A fine is a punishment. Given the situation, I think that fits the crime much better.