Does resiliency as an adult require enduring hardship as a child?

Many people assume that having faced great hardship is a necessary part of having resiliency -- meaning: the ability to withstand great challenges in the future. These people think that if you have faced less-than-average hardship in your youth, that makes you soft, spoiled, pampered, and weak, and therefore ill-equipped to face challenges throughout your adulthood. As an extreme (but, sadly, real) example, I have a relative who insists to me, "All of the men I have met who attended private school are weak and naive. In their private schools, they were able to leave their belongings unattended without fear of their belongings being stolen. That's not the real world! By contrast, the public school we attended is the school of hard knocks that shows you the Real World. We remember, all too well, that when anyone left possessions unattended, the norm was for the possession to be stolen. That's Real Life. That builds character and gave me a thicker skin. That's why, when I have children, I will send them to public school to toughen them up. I refuse to raise privileged weaklings." I seethe and feel tempted to respond, "What if you got really drunk and beat up your children? Following the logic of your assumptions, wouldn't that toughen them up even further?" Why are these assumptions about hardship so prevalent? How can a person develop great discipline, stamina, and fortitude absent hardship and cruelty? What can be done to combat the idea that hardship in youth is necessary for strength and resilience as an adult?