The boy you called gay today? He just committed suicide. 
The girl you just called fat? She's overdosing on diet pills. 
The girl you just called ugly? She spends hours putting makeup on so people will like her. 
The boy you just tripped? He is abused enough at home.
See that man with the ugly scars? He fought for his country. 
The guy you just made fun of for crying? His mother is dying. 
Everyone has a different backstory, many of which you can't see. Don't judge someone until you actually know them. 

People are people so treat them as such!