“As a filmmaker, I am compelled to stay hidden in the background, restrained, moderate, balanced, judicious, neutral even,” says filmmaker, educator, historian, and gentleman Raoul Peck about a half-hour into the first chapter of “Exterminate All the Brutes,” his new HBO docuseries. “You learn to avoid becoming the subject of your film. It’s not about you, unless the story is bigger than you. In that case, you go for broke. Neutrality is not an option, and those who seek history with an upbeat ending, redemption, or reconciliation may search in vain. Such a conclusion cannot be expected.”