I can't think of a strategy more antithetical to the founding principles (even while we're being told how fundamentally American uncontrolled immigration is).
Like another poster said, I'm also ready for a good dispute. I'm just afraid it will be over before a challenge can be mounted. It may already be over.
A number of reasons:
1) They attribute the two World Wars to nationalism so they want to destroy national identity;
2) They honestly believe that various people and cultures are equal and can live side by side in a Utopia;
3) White guilt;
4) They correctly believe that the new immigrants are more apt to vote for their statist agenda;
5) They are controlled by globalists who want to create a global identity so as to be able to sell their goods to more people.
I'm sure that I'm missing more legitimate reasons, so feel free to add to the list.