I used to be a laissez-faire libertarian on immigration but I have really stepped away from that because people really underestimate all the hidden costs that illegal immigration has on our system, from depressed wages ("jobs Americans won't do" is an ever-expanding category as a result) to increased health care costs to costs in our criminal system. It results in taxes that fall disproportionately on the middle and lower classes because (1) the rich benefit from the cheap labor to do their landscaping, cooking and child supervision for them, and (2) they can absorb the added costs throughout the system.

It goes back to the basic proposition that you can't have a welfare state and open borders (unless your welfare state is shittier than everyone around you).