***The most effective question to ask of any pro-illegal is simply: why do you oppose the rule of law? If we, as a nation, wish to modify/amend our laws, why not pursue this through normal democratic channels? Selective enforcement is corruption defined - it's how republican forms of government corrode and fail.
***
I think the answer is they employ them and they don't want to pay an American a higher wage.
I would respectfully disagree - most employers employ illegals because it's a reverse arms race - to the bottom of the wage scale. If they can't competitively bid contracts, then they don't get the jobs.
No, I think some of the pro-illegals are political functionaries in various levels of Fed/State/Local governments. To paraphrase Franklin in terms of GOP stalwarts: "We must all hang together (with Bush), or assuredly we shall all hang separately (have to get a new job)".