Christians are called to obey the law, even unjust laws (this is why I keep bringing up Philemon). In that sense I agree - illegal immigration is a sin. But only because of the legal status, not because of the underlying morality of the act. It is very different from child abuse and adultury.
Here we are working in our capacity as voters. And there is no underlying sin beneath the immigration laws - unlike adultury and child abuse. As such, as voters we are morally called upon to grant amnesty.
Number one...it's ILLEGAL immigration we are speaking to....
Number two....I believe the 8th Commandment deals with "stealing"....is it not a sin to assist those trying to "steal" citizenship???