Why is ACLU, and other groups so against strict immigration laws?

Because the US was based on immigration. It was made for people who needed to go somehwere lese, weather it's because they are suffering where they are, or because they just don't like it. If you aren't 100% Native American, your ancestors were immigrants that probably, too, wanted to come to the US to look for better jobs and better life. So limiting immigration now just because you don't want other people doing it? that's not racism, that's hypocrisy.