That line you quote has them dealing with the the benefits.
I don't think that the case has been made that immigration, legal or illegal, is much of an economic benefit to the nation as a whole. There may be certain industries where its crucial, but the biggest study done to date (that I'm aware of) was back in the mid-late 90s by the National Academy of Sciences. It put the net effects of immigration as positive...to the whopping tune of one tenth of one percent of GDP, or in other words, nothing.
"It put the net effects of immigration as positive...to the whopping tune of one tenth of one percent of GDP, or in other words, nothing."
That's certainly a different tune than the sky is falling I've heard on other immigration threads.