I'm a big believer in facts and data. If you look at the yields from the first nuclear tests in all new nuclear powers, including NK's test of a so-called hydrogen bomb a few weeks ago, they tend to be comparable to or less than Hiroshima/Nagasaki. Unless ISIS/Daesh/AlQaeda/Obama'sMinions get a nuke from a power that has conducted multiple tests, we know how well new designs based on theory work. My point is not that a nuclear attack would be no big deal but that survival is perhaps a 50-50 chance and perhaps better.
There would be hundreds of thousands and possibly millions dead (NYC), many burned and wounded, and many at least temporarily deafened. Every family within miles would be affected, as would all public services and all jobs in the area. But my family and his would (mostly?) survive, and many (most?) of my friends and his would survive. I don't like unrealistically low or high expectations; I like realism.
Tell all that to this guy whose worried about his family, himself, and his property : butterdezillion
I’m sure he will be comforted by your data, facts and realism ...