Like usual, the unicorn's entire argument is based on someone else's ideas and writings. Unfortunately we live in a world where many people don't know how to think for themselves and assume everything they read is fact. Sometimes even misinterpreting the meaning behind that document as well due to their lack of ability to understand. It is a known fact in Arizona (along as many other places) that illegal aliens take jobs for lower pay stealing original legal resident’s opportunity for income (jobs). If you deny this then you are probably still in grade school and don’t have any real world experience with jobs/illegal aliens.
Illegal aliens do work, yes; it's almost always work other people
don't want to do. At the same time, they're demanding goods and services just like anyone else, and as a result grow the economy.
The reason I cited Factcheck.org is that, first of all, as a general rule of thumb, they are a very reliable fact-checking source, particularly for widely-politicized claims, and second of all, economics is difficult and often incredibly counterintuitive. First impressions are often (read: almost always) wrong, and the results can be incredibly puzzling. For example, it doesn't seem like paying someone to dig up and fill in a hole would grow the economy, but if that person is poor, it has as a result that that person has more disposable income, and can reinvest it in the community. Or how about the paradox of thrift? That one's kinda weird.
But really, all of this doesn't matter. Countering a reputable source (which, itself, cites countless other experts) with "It is a known fact" (and
nothing else) is just weak sauce.