Luckily, there are only a handful of pro-amnesty posters around that I've seen. They fall into two categories. About half are Libertarians who like open borders because they short-sightedly believe that a flood of cheap Third World immigrant labor is "good for business." Then you have certain misguided religious individuals who think that "we're all God's children" means that we should welcome all of the Third World's dregs to our doorstep.
I suppose you also get a third category who use the stale old "you can't possibly deport them all" line - which is just cover for whichever of the two above their real agenda is (notice that they never use the "you'll never catch them all" line to argue for amnesty on behalf of any other kind of law-breaker).
I don’t care what category they fall into, they are STUPID and their opinion is ridiculous.