They never left, much like the Europeans who were working off their debt in the "New World".
Even if you go back to the 1800s you still can't compare the illegals of today to the people coming through Ellis Island. There is a system in place for a reason and the sooner politicians start enforcing it the better this country, with states such as CA, will have a lot more money and a lot less problems. There should be no problems. You aren't legal, you don't stay. It really is that black and white.
Why am I not surprised that you see this in terms of black & white?
No... Your reasoning is the problem.
It is NOT black and white. There are infinite shades of grey and until you grasp that, it will never be worked out to yours or anyone else's satisfaction. What will happen after... will you drop a bunch of B52's on Mexico or Chile in order to get their produce, ...'cause Lord knows you wouldn't have any of your own.