I can certainly think of many examples of secrets that people keep secret out of self-interest and attempt to justify by claiming they are doing it in the best interests of the ignorant party. In most such cases the 'more harm than good' would accrue to the party requesting the keeping of the secret rather than the party from whom the secret is being withheld.

But this is the way to think of WrongBot's claim. The conscious you, the part over which you have deliberate control, is but a small part of the goal-seeking activity that goes on in your brain. Some of that goal-seeking activity is guided by interests that aren't really yours. Sometimes you ought to ignore the interests of these other agents in your brain. There is some possibility that you should sometimes do this by keeping information from reaching those other agents, even though this means keeping the information from yourself as well.