RE: goofy post by Kevin MacDonald.
I'll give the conclusion in advance: Gilder appears to have as much Southern ancestry as New England ancestry, and most of his ancestors hailed from the Mid-Atlantic states. Here are his great-grandparents:
8. Richard Watson Gilder (b. 1844, New Jersey): Son of a Methodist clergyman. New Jersey and Delaware ancestry. Talks about his ancestors (including one with "Huguenot blood") here, failing to mention any New England Puritans.
9. Sarah Helena de Kay (b. 1846, New York): New York ancestry (including Dutch and apparently Scotch-Irish).
10. Louis Comfort Tiffany (b. 1848, New York): Finally someone of New England ancestry. But he lived in New York and was, I believe, an Episcopalian.
11. Louise Wakeman Knox (b. 1851, New Jersey): Daughter of a Presbyterian and Dutch Reformed clergyman; of apparent Scotch-Irish ancestry.
12. Reese Fell Alsop (b. 1837, Indiana): Episcopalian clergyman. Pennsylvania ancestry.
13. Mary Lee Spring (b. 1848, Pennsylvania): Father born in New York. Irish and Scotch-Irish Pennsylvania ancestry on mother's side.
14. Robert Williams Chapin (b. 1855, Massachusetts): Ancestry appears to be half New England, half Southern.
15. Adele Le Bourgeois (b. 1862, Louisiana): French name. Grew up on family's plantation.
I was unable to identify any Congregationalist or Unitarian among Gilder's recent ancestors. Gilder is himself an Episcopalian, and he founded the Discovery Institute with his Papist college roommate, who seems to have similar views on Israel. I find it rather hard to believe that internalized guilt passed down from the 1.5/8 of his ancestors who were of New England Puritan stock explains Gilder's philosemitism.
People with more New England ancestry than Gilder: Henry Adams, Brooks Adams, Henry Cabot Lodge, Charles Davenport, A. Lawrence Lowell, H.P. Lovecraft, Henry Fairfield Osborn, Madison Grant, Lothrop Stoddard, Carleton Putnam, etc.