Strawman. I don't know of any current politician who is advocating Operation Wetback 2 (Eisenhower). Speaking of compassion, do we let in 7 billion people who have not come here yet? In effect, that is what another amnesty will say to those people.
Not trying to pile on, but is this the same defense we use when the sole wage-earner in a household has to go to prison for a criminal act?
A case in point, is it the U. S. government or other citizens who created the circumstances these children will have to deal with? NO! It is the person who has violated the law, that has caused whatever ramifications their act has resulted in.
Another way to look at this, is that the U. S. is poaching Mexican citizens. We have educated many of these people's children. Those children are an asset of Mexico, not the United States.
Is it our nation's right to steal useful assets that Mexico needs to improve it circumstances? Actually..., no.