The US had indentured servitude before it had slavery. In fact, it was an African indentured servant (Anthony Johnson) arguing in Virginia courts that he had the legal right to own his own African indentured servant for life that led to slavery becoming an institution in the US to begin with, so if we follow your logic about deporting illegal immigrants being a bad thing, the only logical conclusion is that the left wants to restore slavery in the US, since we've been done this road before.