Do you have a decent source confirming that "To Set It Right" never aired? That detail is not mentioned in either Roddenberry biography from '94. All I can find are references online, none of them cited, and a somewhat contradictory account from Marc Cushman and Susan Osborn claiming that NBC didn't want to air the episode, but that the NAACP successfully intervened and changed the network's mind. As you can imagine, I give no credence to either source.
I was just going by Wikipedia. But IMDb says it did air on Feb. 22, 1964. Neither is a particularly reliable source.
Other data points:
- Nichelle Nichols mentions filming the episode in her memoir, but says nothing about NBC refusing to broadcast it, or any NAACP action to change their mind. If the episode was pulled, this surely is an odd omission.
- the February 18, 1964 issue of Daily Variety has an article indicating that the episode would air on NBC without a DOD seal of approval (the issue with the Pentagon is well-documented; they did not give script approval and withdrew their support for the series following the episode).
- the February 24, 1964 issue of Daily Variety has a positive review of the show.
(I don't have access to then full Variety articles, just snippets.)
It seems likely that the episode aired as planned, and that all the information circulating about it being unaired is erroneous.