The Barnes Foundation owns a treasure trove of Impressionist, Post-Impressionist, and early Modern art. Dr. Barnes accumulated this at a time when the art community (or at least the elites) of Philadelphia derided these works as "primitive" and his enthusiasm as misguided. So he set up his foundation as an educational institution, not a museum, with restrictions on how often the collection was available to the public. He had a grudge, and tried to set up stipulations that would prevent his collection from being moved, separated, lent, or controlled by the sort of people by whom he'd been snubbed. (Particularly the Annenbergs! Whose charitable trust is a backer of the new museum site.) The bylaws went so far as to require that "at no time shall there be any society functions commonly designated receptions, tea parties, dinners, banquets, dances, musicales, or similar affair."
The documentary makes a solid case that Barnes had a vision for his foundation, and that vision has been subverted. It's less clear on building the moral case that this was an institution that deserved to be preserved in its original form, although the former students and teachers featured obviously believe so. Should we let the grudges of the dead outweigh the good of the living? Everybody would want their wishes respected after death, so there is a moral weight towards behaving that way yourself--- but that directive, like the property rights involved, is not an absolute. (Which is not to condone any back-door shenanigans and deal-making that seem to have taken place. But foundations must be living institutions, not dead ones.)
I think that argument is an interesting one--- "public benefit" should not always win--- but it's also worth considering whether and where Dr. Barnes erred in trying to preserve his legacy.
Dr. Barnes stipulated that the trustees be nominated by Lincoln University, a historically black college whose president at the time was a friend of his. He believed that this would maintain the foundation's independence from the political and financial elites of Philadelphia. (Lincoln was the alma mater of Cab Calloway and Thurgood Marshall, among other notables.) This belief proved naive. Lincoln University became a state institution in 1972, and thus vulnerable to political pressure. It had its own educational agenda, not tied to the beliefs of Dr. Barnes. And a college which is out-of-power in 1951 may be a stepping-stone for ambitious people by the turn of the century.
Barnes and his successor Violette de Mazia failed to ensure that the control of the institution resided among those with a stake in the status quo. Barnes himself had no children. Although I can think of some glaring literary counterexamples, family could more likely to respect the wishes of the deceased and share his (or her) values. (On the other hand, somebody who isn't famous may seek greater prominence by exactly the sort of hobnobbing with the elites that Barnes wanted to avoid.) There were no trustees who were appointed from within the institution itself. Barnes might have been better off selecting an institution in a different state. He certainly should have diversified the source of board members.
Barnes' instructions also failed to take into account the possibility that his endowment might be inadequate for maintenance and upkeep. Or that, if adequate, it might be portrayed otherwise for the purposes of "saving" the collection. Clear positive instructions, rather than negative prohibitions, may have given the trustees options that were still in keeping with Barnes' wishes. Instead those seeking changes were able to make a court case that the changes were necessary and urgent.
It may be simply impossible for an institution with billions of dollars of assets to remain as the founder envisioned. Who knows what the Gates Foundation will look like 90 years after its creation? But I think Barnes failed to make the scope of his protections match the value of his collection--- protections need to be not just legal but social and cultural as well.