Why do both over-discipline and under-discipline of children produce rebels?
Over-discipline and under-discipline both produce rebels because discipline must be temperate, maintaining a middle balance rather than swinging to either extreme. Going too far right or too far left in disciplining children results in a bunch of rebels; only the middle-of-the-road, temperate approach avoids that outcome.
Les teaches that being temperate means you maintain a balance: you don't go clear off to the right and you don't go clear off to the left; you maintain a middle balance. He says he has used this example in his classes over and over, and it works in disciplining your kids. You cannot over-discipline, or you're going to have a bunch of rebels. You cannot under-discipline, or you're also going to have a bunch of rebels. Instead, you have to maintain that middle-of-the-road, temperate idea of discipline. He applies the same principle to business and to running the Christian life: extremes on either side bring failure, but maintaining balance—being temperate in all things—is the right path.