, iI have the 1981 and 1993 editions in front of me and in both he stops short of saying that the fans were primarily responsible for the renewal but implies that they played a role in the decision.
He cites a number of sources when re-telling the letter writing story, including a report from Newsday in which NBC admits receiving 16k letters of protest. Roddenberry claimed 6k a week. The same article has a quote from Roddenberry denying network accusations that he was responsible for the campaign.
There's also a report from the NYT, cited by Asherman, that reports that the NYC affiliate interrupted a ST broadcast in 1969 to report election results and was flooded with calls. No numbers on how many though.
The only reference he has with numbers for in person protests is a 1968 Newsweek article about 500 students from Cal Tech demonstrating at the NBC offices in Burbank.
So, yeah, no evidence in the Compendium to support even 100k letters of support, and any in person demonstrations were relatively modest.
Whether or not Roddenberry was behind the letter writing...maybe? Seems like that could be a rumor NBC started to discredit him (but why would they do that?), or he was behind it, or it was totally independent. That particular topic has been beaten to death, though, so there's no need to go into a detailed re=hashing.
Some of the information above mirrors passages in The World of Star Trek (1973), including NBC telling TV Guide it had received 200,000 pieces of mail, Bjo Trimble informed that the overload of mail was so great, it was too much for NBC's machines to handle, but at the end of it all, on page 168, Trimble said:
So, if one chooses to believe the Gerrold book and the references within, the letter-writing campaign was not organic, but orchestrated, whether Roddenbeerry admitted it or not."Eventually, we had an NBC man from Burbank come out and talk to us on the Star Trek set one night, and he asked us if we would tell them how we had done it. How we reached so many people so fast? And how we gotten the information to them about how to address the envelope and how to phrase the letter politely? Of course, we didn't tell him. We might have to do it again someday."
That's a pretty massive difference in story though. 200k letters and a complete overload of NBC's ability to process vs. 16k and a minor nuisance. I do agree with the interp that Roddenberry was at least in contact with Trimble.