Teaching your child to never say “no” to an authority is not preparing them for adulthood. At all. Instead, it prepares them to fall into patterns of abuse or dysfunction. It prepares them to obey an unreasonable or abusive boss rather than going to HR or quitting and finding another job. And so forth. Children need to know that they can say “no” to those in authority over them, both as children and, in the future, as adults. 

In the present, before they grow up, teaching children not to say “no” to an adult makes them perfect targets for abusers. A child who has been taught never—ever—to say “no” to an adult is laid open and ready for grooming and abuse. Children very badly need to know that they can say “no” to adults.