I agree with you, they are criminals in that sense, but they're not scum. They're just trying to make a living, and as I've mentioned before, migrating legally to the US is a pain, a long process that takes a lot of time and money, which is why most immigrants are illegal.
You won't find anywhere that I have called them scum. I also know that the process is a long one - but it is the process that we currently have in place and as such they must abide by it unless they wish to be treated as criminals.