I think Ben may gain assurance because he's been told what the future is. Maybe by Widmore, whom I suspect is a time traveler, maybe by Richard. He may have gained the respect of the Others by his ability to know how things would turn out; he allowed himself to be captured by the Losties because he knew they wouldn't kill him; he supposed that Keamy couldn't kill Alex, and when he did, the Others lost faith in his prescient abilities. That's when he knew he had to give up leadership and hand it over to Locke. He visited Widmore, and accused him of changing the rules. It seems to me that Widmore is the one who told Ben the rules. Either he makes the rules, or has been given the rules by someone. I suspect that only those in the future, who know how things turned out, could know the rules. That's what makes me think Widmore is from the future. It also makes me think that he is trying to shape the future in a malevolent way, possibly to his own benefit. If so, that would make him the main antagonist in the show, and Ben could be a potential protagonist. It's impossible yet to say the roles of Richard, Ammadon, or Mrs. Hawking, all of whom I believe are time travelers.