Any consistent bad behavior is contagious. Uncorrected bad attitudes in others' children have caused me to limit and even replace their interaction with my children with positive activities. Uncorrected bad behaviors ramp up that response to the children, and so naturally, to their parents.
The specifics are rooted in a choice to maintain high values/morals in one's children. That begins by evaluating self and being willing to step outside what some consider the social norm re children's attitudes/actions for the sake of one's children's future.
Remembering that the goal for them to become responsible adults does not conflict with letting them have a great childhood is easy when we realize that we have the ability and the responsibility to own the direction they need to go in order to live out happy, productive, and satisfied lives.
An old gardener's rule comes to mind: early bloom, early rot. Protecting their young childhood from much of what even our youngest are exposed to in entertainment, for instance, allows them to view what they are exposed to later in life through more mature eyes and from the perspective of what they are taught is safe, and right, and useful, and helpful, and… when they are young.
Parents don't want to do this because it means depriving themselves to a great extent, but that does not change the truth. Parents don't want to plan ahead and do the work of saying no to what is happening to children in the culture because they don't see the need, they don't want to give up more of their time, they worry about others seeing them as different, and more.
I just heard a quick report on a study about what children want for Christmas. Most of the time they would simply like to have more time with their parents. The real question is wrapped up in whether parents will continue to go in debt for presents, or step back consider what is important to the children and their well-being. The same goes for friendships.