BuzzFeed's Leonora Epstein uncovered this blog post from the blog My Star Trek Scrapbook, which features a letter from a 1968 issue of the defunct teen magazine FaVE! In a letter addressed to Mr. Spock, a young biracial girl laments that she doesn't fit in with either her black or her white peers.
"I know that you are half Vulcan and half human and you have suffered because of this," the girl named F.C. wrote. "My mother is Negro and my father is white and I am told this makes me a half-breed. ... I guess I'll never have any friends."
Nimoy was so moved by the letter that he responded at length in the next issue. "[Spock] said to himself: 'Not everyone will like me,' " Nimoy wrote. "But there will be those who will accept me just for who I am."