Hello; Not convinced that the nature of children has changed over time. I can give examples of cruel behavior from a ways back. I tend to think that the difference is more the way our society has over several decades changed the way poor behavior is delt with. In terms of a consequence for bad behavior children are allowed to do pretty much what they want without any untill they reach the age of 18. There have been several court rulings that have expanded the "rights" of children while other rulings and social practices have been removing responsibility - rights without responsibility/ rights without consequence.
As a poor example, For a time I took part in the scoring of portfolio work of students for each school term. We were trained to ignore spelling and sentence structure as a criteria for scoring. In other words an english teacher was not allowed to downgrade a students paper for missspellingg (Ha -ha) or bad sentence structure. This became the norm for an entire state. The same sort of scoring was applied to the other subjects. Teachers were instructed to avoid negative comments or scoring of a student's work and find some kernel to be positive about. ( enhance their self esteem) To some this allows children to become free spirits and to allows them to develope on their own terms. I am still not sure how this will be an advantage to an illiterate high school graduate when they are seeking a job. We have graduates with good self esteem and very poor job skills.