My gladiator costume is out, because it i'm not Roman or Italian plus it glorifies violence.  
My pirate costume is out since it is trivializes the plight of hostages captured by Somali pirates and it is associated with criminal behaviour and  unauthorized copyright infringement.
My cowboy costume is out since it would be triggering to native americans.
I won't even mention a friend that went as Donald Trump last year because of the ensuing uproar...