How much of elite enthusiasm in the Northeast for opening the borders further to, among other worthy goals, save Mexicans from starvation is a transmutation of the old Yankee missionary impulse? In the 19th and early 20th Centuries, the wealthier northern Protestant denominations did a lot of missionary work abroad, such as in Hawaii, China, and the Arab world. In Hawaii, the Yankees started off doing good and wound up doing well, while in China they got kicked out, one and all.
Eventually, the high WASP progressives tired of Christian proselytizing, and also realized they weren't always as welcome in other lands as they had assumed. So, rather than go to heathen lands to uplift the benighted, why not just have the vibrantly diverse come here to be uplifted? The uplift urge continues.
Of course, little of the traditional northeastern Yankee uplift effort is currently directed at immigrants, which would be insensitive. Instead, it is focused upon you unenlightened nativist yahoos for not being persuaded by the browbeating of your betters that allowing mass immigration is your post-Christian duty.
Commenter David M. immediately replies (on my own blog):
You know, I don't think they would really want us nativist yahoos to change our ways. We give them an enemy and someone to feel morally superior to.
I don't think that they want the immigrants to change either. They would rather that immigrants remain oppressed noble savages that they can protect from the evil nativists. As long as they remain foreign and distant (but simultaneously resident in the U.S.) they serve as excellent blank slates to project victimhood onto, while their actual behavior and beliefs remain totally irrelevant. If on the other hand they behave like white Americans (ala George Zimmerman) then they become real human beings, and must be lumped into the "good" or "evil" categories based on whether they have the right opinions and cultural habits.