It's amazing how many idiots on the streets of America that approve of the scenario in the opening post.
A lot of liberals like it because they like any thing contrary to traditional American values that they can call and underdog and feel better about themselves supporting. They also believe that allowing a lot in here from third world countries will give them a permanent political advantage, particularly when given amnesty. In the meantime, they just need to keep fighting voter ID laws and keep on cheating. The stats indicate that hispanic/latino immigrants are more likely to vote Democrat.
Big corporations and small ones in landscaping, ag, construction, food processing, food service, etc. that use a lot of relatively unskilled labor like it too. They have a gray market supply of labor that is more reliable than the lower class of US citizens and they are not vociferous about higher wages.