There are three sides: illegal immigrants, those with a legal right to work in the U.S. and employers. Illegal immigration benefits immigrants and employers but hurts legal residents. It doesn’t take a genius to see why. Furthermore, since legal residents are an overwhelming majority of the population (for now), the overall effect on the economy is negative, as documented
here and in many other studies.
Illegal aliens are not an essential part of our economy. Our economy was doing just fine before illegal immigration - the lettuce got picked, the houses got built, the floors got swept, etc. The difference is, you used to be able to make a living doing those things, and now you can’t. Tolerance of illegal immigration is essentially a welfare program for foreigners, paid for by American taxpayers and depressed American wages.
On the subject of whether illegal aliens are entitled to Social Security: Not yet, but if the Bush Administration has its way, they soon will. Illegal Mexican aliens who used counterfeit social security cards will be given social security benefits as if they had earned them legally. Americans who do that don’t get social security - they get sent to jail for fraud.