Denigrating a 17-year old girl by the comments about her weight is not 'common decency' in my judgement.  Nor is the comment about 'cocaine useage' by another young girl.  It wouldn't be 'common decency' by another 17 year old.  

By two adult and supposed "mentors" and role models, it is completely disgusting behavior.  

Maybe you think it is fine.  Maybe you think there is some cultural excuse for it.  

You have your standards for behavior; and I have mine.