It means supporting each other, and defending each other. It means cohering to a shared set of values, and it means respecting the laws we have all agreed on.
Throwing open the doors to all comers is in complete contradiction to all that. Immigrants are abandoning their fellow citizens, and often their families. They’re not coming here to give more than they get — if that’s what they were seeking they could probably have found it in their old countries. They’re — quite rationally, and quite admirably in many cases — trying to come here for a better deal, but as US citizens we don’t have to accept their deal. We have a stake as well, and one of the obligations of a citizen is to respect that stake.
I’m a good Christian too, but I give to others from my own time, my own labor and my own resources. I sacrifice myself for others — I don’t force my neighbors to sacrifice in my stead.
As a Christian, I’m unwilling to let the lifeboat get dragged under because it can’t support all those trying to get in.