I'm not sure if I agree with that theory.
A lot of us children of the eighties have lived through a rebuild, and we know they suck. A lot of us aren't anxious to see a rebuild. If the central argument is that more mature fans recognize the necessity of them, isn't the counterargument that no "rebuild" in Celtics history has been particularly successful? The only title we've won in the last 25+ years was due to the win now approach.
I can see some younger fans getting irrationally attached to Rondo, but I think plenty of older fans appreciated his game. I mean, I personally think it's sad that there were so many "anti-Rondo" fans, meaning fans that actively seemed to root against him. Even for those of us who noticed his flaws, I would hope that we could also see his amazing strengths.
Also, of course, even those fans who thought that it made sense to move Rondo don't necessarily have to like the return we got, which was somewhere between manure and garbage.