I occasionally hear it from friends - not in a truly mean or insulting way, but just more of a 'why do you go to Disney as a single adult? What's the draw?'. So I've actually taken the opportunity to educate quite a few friends by inviting them along. Over the years, I've converted a co-worker, and three friends who hadn't been to Disney since they were kids and thought it was all about rides and kiddies. We stayed at nice resorts, we slept in, took boat transportation, hit the good restaurants, I gave them some Disney inside information on theming and design in the parks and how things were researched and built, various Easter eggs found throughout, etc, we visited the bars and various resorts, and stayed to park close most nights. After that trip, they understood that Disney can be a draw for adults too - and ALL of them have returned multiple times since, both with and without me.
The best thing about it is that the few friends who haven't taken me up on the offer are quiet about it now - because they're no longer just asking me why I would want to go to Disney as an adult, but 4-5 other friends who are now 'on my side'.