Here is the jist of the argument IMHO.
To come here LEGALLY takes time and money, at the very least.
To come here ILLEGALLY takes no time, and no money unless you are smuggled in by an organized gang.
To come here LEGALLY means following the established laws as outlined by the Congress and enforced by the Executive branch.
To come here ILLEGALLY menas following NO laws except how to not get caught.
Now, should either group have the same rights, ONCE HERE, to live, work, receive social services, etc, ASIDE from the fact that neither group have become naturalized citizens, with voting privaledges.
Any guest worker plan has to penalize in some way the folks who have already broken the law. There is no way around it. The majority of folks will not accept anything less.
Now, we have to agree on the penalties, and the means of enforcement.
Haven't they already been penalized by paying into Social Security, often under fake SSNs, with money that they will never be able to use? They will never be able to draw Social Security in spite of perhaps paying into the system for 20-30 years. That's a huge fine right off the bat.
They also have paid the unemployment tax and can never draw unemployment payments for any time they are out of work. That's another already paid-up fine.