Left wingers overwhelmingly support immigration of poor people, from poor nations. They think these people would benefit the most out of immigrating to the US. They too, like the right wingers, despise white collar workers immigrating here, since that'd mean more competition for high paying jobs.

They know that recent immigrants from poorer countries, do not have the education and English language skills to break into white collar jobs, and will mostly work in low paying jobs for their whole career. The white collar immigrants can break into all these jobs, and that is something that they see as a danger.