I'm seeking occurrences in history where people or organizations did some activity, but witnesses who would speak about the activity, would be considered insane, because of the unlikely nature of the event. Because of this 'deterrent effect', the activity could be continued.
It can be crimes or another event that fits the description. The term 'activity' can be interpreted freely. It can also be a 'cover up' from the organization, in the sense that people 'act as if'. People can be dressed or act in a way that deters them to report an accompanying event. In that way, the accompanying activity isn't reported because of the 'cover up'.