Another problem of secrecy is that it robs people of the ability to object.

When it's secret, you don't know that something is being done, and if you can see something happening you don't know why. Happenstance, coincidence, deliberate action? Who knows, and who can argue when you don't know what to argue against or when. (In extreme cases, even who to argue with.)

(I guess the problem of secrecy may not have been entirely that, after all.)