I tend to think that quantity is the main problem.
I've heard that about half of the illegal aliens are from Hispanic countries. Most people don't realize how many illegals here are from Europe, Canada, Australia, Asian countries, etc.
I agree that aggregate quantity is a problem, but not relative quantities. One could say that there are less than 0.1% of illegals who drive a AMC Gremlins. Should we therefore not worry about illegals who drive AMC Gremlins? If we want to reduce the huge aggregate number of illegals, we shouldn't ignore small subsets which make up the whole.