I agree. When I was 15, I wouldn't have dreamed of treating anyone that way, and neither would most of the kids I knew. The kids who were mean weren't as cruel and vicious as they seem to be today.
A 15 year old is plenty old enough to know how to treat others properly.
While I agree 15 year olds should show restraint in tongue as well as fists, my memory is the 13 to 14 year olds mixed with the “pack mentaility” and spiced with newly arrived hormornes can be a potent elixir that can cause serious harm. From my life, I have seen a lot of bullies grow out of the bully stage, but I have noticed a lot of bullied individuals become the worst people to work with in adulthood. Once a bullied individual gains power their propensity to bully others is overwhelming. This is the lasting damage of the bully to bullied phenomena in my opinion.