There has been a growing trend of kids being extremely disrespectful to adults, and that is not surprising. These kids have no respect for authority and you can boil it down to one cause. This cause is either very poor parenting or a complete lack of parenting.
Kids learn what is proper and what isn’t proper from their environment and caretakers. When the caretakers are dysfunctional and cannot teach them proper behavior fit for society, you end up with a highly disrespectful kid. It’s no surprise with the growing number of single mothers and the destruction of the nuclear family. As an adult, you should no longer reasonably expect an unruly teen to respect your adult authority.