Using a nuke to fight off a tide of refugees is like bringing a grenade to a fist fight. Do you think the people who are already here are going to tolerate the wholesale slaughter of their family members who are trying to rejoin them? What about all of their friends? No. If we don't find some way to rescue everybody we will be torn apart by civil war.
If by "here" you mean North America and Western Europe then yes, they will pay the price for their diversity. Places like Japan and China that people say are "xenophobic" might turn out to have the better survival strategy.
