I think the cancellation, if caused by political pressure (as seems likely) is an unfortunate example of self-censorship. On the other hand, it was brave of Nikon to propose the exhibition in the first place.
After all, how many US corporates have sponsored exhibitions of Dorothea Lange's photographs of the internment of American citizens of Japanese descent during WWII? None, as far as I am aware. It is an unfortunate fact that all nations have periods in their history that, if presented accurately, show them in a poor light, and which generally are swept under the carpet by government as well as by civil society. Another example would be the atrocities committed by the British during the anti-colonial uprisings in Kenya which are only now coming to light since records were deliberately destroyed, and those that were not were hidden for many years in defiance of access to information legislation. And let me not fail to mention the horrific human rights abuses of my own country's recent past.
I'm not saying that we should not attempt to shine a light on these sad chapters in all our nations' histories. Certainly we must, for if we do not learn from history it is bound to repeat itself. But it is perhaps best to start at home, with introspection, since "why beholdest thou the mote that is in thy brother's eye, but considerest not the beam that is in thine own eye?" (Matthew 7:3).