Michael Mann and Eric Roth based the screenplay for The Insider on Marie Brenner's article "The Man Who Knew Too Much." Brenner interviewed both Jeffrey Wigand and Lowell Bergman extensively during the time that the 60 Minutes crisis was going on at CBS. Brenner's initial focus for the article was Wigand -- his tale of being a whistleblower and the threats he was reportedly receiving from Brown & Willamson. But during her research, Brenner saw another drama that was building simultaneously. The second storyline dealt with Bergman's battle with CBS to air the Wigand interview.
When filming, Mann stuck closely to Bergman's version of what happened between Wigand, Brown & Williamson, and 60 Minutes. In addition, he enlisted the help of both Bergman and Wigand in order to be as accurate as possible. Even before The Insider was released, controversy swirled over its representation of some of the film's key figures. Brown & Williamson complained that it is portrayed harshly in the film as the result of accusations made by Wigand that have never been substantiated. 60 Minutes' Mike Wallace also disliked how he was portrayed as a "corporate lackey." The problem is that much of the story cannot ever be proven to be 100% true, because it is based on he-said/she-said conversations that took place behind closed doors. Thus, Mann's film supported Wigand's and Bergman's views of what happened, which inevitably made Wallace and B&W angry.