A pitch is an outcast for something. The preliminary draw-up of a plan, proposal or article that will guide what the finished product looks like. You can also "pitch an idea" to someone, for example. Insane in this context does not mean that he literally loses his mind, he has not had a mental breakdown. The word is used to emphasize the difference between his new strategy for marketing (which is outrageous because it is very direct) and the normal way of marketing (polite, not very direct). Not having seen the movie, I would guess that the phrase "creates an agency out of people from an insane asylum." means that the main character literally hires people from an insane asylum to work in his ad agency (because of the success of his initial, accidental marketing strategy - when he "went insane")