" I think the major kick against the inflow of immigrants is the Catholic culture"
Tell us you're joking. That's a weaker and nastier arguement than, "they're good for the economy".
Besides, I've not seen anyone complain about "immigration". We're talking about ILLEGAL ALIENS, and I don't care what religion they pretend to practice.
This country got along just fine without immigration laws for the first century. We didn't start limiting immigration until the late 1800's, early 1900's, and that was mostly because of eugenics theory promulgated by Darwin, Sanger and their ilk.
I have yet to see one good argument for being seriously concerned about immigration, legal or illegal.