"Batman v Superman: Dawn of Justice" director Zack Snyder says he's still trying to understand the criticism lobbed at his previous film, 2013's "Man of Steel," during which Superman (Henry Cavill) killed the genocidal General Zod (Michael Shannon) after a battle that destroyed much of Metropolis and snuffed out thousands of people.

For many fans of the DC Comics icon, Superman isn't supposed to kill people, and he must do whatever he can to save every innocent bystander. However, Snyder considers himself...