Filmmaker Ronald F. Maxwell is considered by some to be the foremost cinematic interpreter of the American Civil War. With his last two films, “Gettysburg” and “Gods and Generals,” Maxwell has given us a glimpse at the heroism and sacrifice of men and women on the battlefields. With these films, he has examined how good, ethical, and moral people, could choose to go to war for what they believed in. Now, with his latest foray into the era, he has chosen to examine the opposite spectrum: how good people could choose not to go to war, or show support for the conflict. The idea of speaking out against war, even when it is not popular to do so, lies at the heart of his latest endeavor: “Copperhead.”