How does it have a negative effect on the economy.
People say that they take away jobs from people, but in my observation it seems as though the jobs they "take away" are often jobs that many consider themselves too good to take? At least for that wage.
If anything, I find the economy argument bunk, because cheaper labour means that goods get produced cheaper, and it adheres more to the lassiez-faire capitalist ideology, which has a pretty good track record for growing an economy.