You can only expect this sort of behavior from the insane or extremely stupid.
If dad is a drug addict or a sex criminal, acknowledging it would shatter the family. The protection of the secret becomes the family’s unifying endeavor. If anyone says anything, it might reveal that everyone is in on the secret. The sick family devotes all necessary energies to collusion—to mutual and self-censorship.
During the past four years, American politics has been dominated by a coalition each of whose members, like codependent kin, has its own investment in group integrity and the power it derives therefrom. The superrich, academia, Islamists, Marxists and the media have colluded to suppress the true and impose the false. Source: freerepublic.com