Illegal aliens are not supposed to be living and working in the United States, they are breaking laws by being present within American borders.
Illegal aliens are not screened for a previous criminal history prior to entering the US.
Illegal aliens' labor is being exploited. They drive down wages, and the jobs that they think no one wants to do used to pay a decent living wage, and were staffed by adolescent, poor and middle class Americans prior to 1986.
Start doing your job Mr. Obama and if you won't then please resign.