I guess I have just had different experience. I'm not saying small telescopes aren't good for public outreach; I'm just saying that in the 20 years I've been doing public outreach, I've had the best results when I use my 22-incher.
One difference may be what we mean by public outreach. I'm not talking about teaching people how to use a telescope, but rather, taking them on a tour of the heavens. They are very different activites. When I do an adult astronomy class I use my 11" Starmaster ELT, 6" Criterion Dynascope and 4.5" Orion Skyquest, for just the reasons that EdZ cites. I would never suggest "teaching someone the ropes" on a 22" scope.
Interestingly, while John Dobson and Bob Summerfield also like to use large telescopes for public outreach, David Levy specifically prefers to use small telescopes. So, I think that either approach can be successful :-)