I agree with all that Bryan says here . A slice from Bryan’s post:
Finally, immigrants probably reduce native support for the welfare state by undermining our group identity. This is a standard story about why the welfare state is smaller in the U.S. than Europe : People happily vote for big government as long as the beneficiaries look like they do.
One of the commenters at Bryan’s posts suggests that neither Bryan nor I – or, by implication, any scholars whose work we point to – have yet to “provide detailed, systematic support” for our premise that substantially liberalized, even open, immigration is a sound policy. One can, of course, always reject any argument as insufficiently detailed and inadequately systematic (“Well, Mr. Gibbon, let us know if and when you finally decide to provide a detailed and systematic argument for the decline of the Roman empire.”)
In my judgment, however, Bryan has blogged on immigration extensively and systematically and with an abundance of details. (Search through the EconLog archives.) I myself have blogged extensively on immigration here at the Cafe, although I don’t pretend to have done so with Bryan’s brilliance, insight, creativity, or knowledge of the full range of the relevant literature. (Search under “Immigration ” in the Categories box in the left margin of the Cafe’s home page.) And both Bryan and I have written elsewhere on immigration; most, if not all, of these other of my immigration writings are linked in various past blog posts.
Bryan and I (and others) have linked to and made use of research in books by scholars such as Jason Riley  and Julian Simon ; we’ve done the same with articles and blog posts by many others, including Stuart Anderson , Shikha Dalmia , Dan Griswold , Vipul Naik , and Alex Nowrasteh, and Ryan Young .
A large quantity of words in arguments hardly guarantees a large quantity of truth or insight in those arguments, but, well, it does at least suggest detailed and systematic inquiry.