My parents are boomers on the cusp of being silents, themselves, and there's definitely some difference between what they percieve and the younger generations. It's hard to say how far back it all goes, really - while the depression and war years were certainly influential in making the culture that overshadowed the rest of the 20th century, stories of harsh discipline are age-old. Perhaps what makes it defining is just the fact that it occurred as a near-universal in the same way that the current pandemic did, and the result was a postwar generation with very sharp differences in attitude.