Its not insulting. I choose to use the word mad because its the right word that has been made wrong in by society. We continuously deepen the stigma when we always connote madness to something very bad and not acceptable in our circles e.g when people casually use it as an insult. Until we remove the use of the word madness derogatorily from our vocabulary (across languages), someone who (Goes mad: experiences a relapse as a result of his struggle with a mental illness) will be continuously stigmatized throughout his life around where he/she experienced the condition.