Pretty much all of those pro-illegal immigration arguments boil down to "economic output is higher with illegal immigrants, also illegal immigrants buy stuff, therefore everyone wins!" To me, that fails to consider where the increased economic output goes. Seeing how corporate profits are higher than ever while wages are stagnant, it's incredibly tough for me to see how it would be a positive for the lower class that need to compete with those illegal immigrants.

edit: Oh, come on, Hacker News. Don't be an echo chamber. I'm not being an asshole, merely stating my viewpoint. Don't downvote me for disagreeing with me, I'm trying to contribute to the conversation.