Question: Maybe this is explained better in the book, or maybe I just wasn't paying attention. But at the end, when Ender killed all the Formics, did he kill any innocents, or were they all involved in the first invasion? Because Ender never mentions innocents being killed, that would be a pretty good argument as to why it was wrong. If they were all involved in the first invasion, I don't see anything wrong with killing aliens that murdered millions of humans.
Question: If Ender would destroy the planet in the simulation, why wouldn't he do it for real? The simulations are supposed to be practice.
Answer: For the same reason when you are playing a video game you will run people over, or shoot them without figuring out who they are. He thought it was the equivalent of a video game, i.e. not real, so he would potentially do things he wouldn't do if he thought it was real. This is the very reason the power structure put them into a real operation while leading them to think it was a simulation, so they would be likely to act when faced with a moral dilemma.
Answer: In the book, Ender had grown disillusioned with military school and was depressed. Destroying the entire Formic homeworld was his attempt to force the school to expel him, by enacting a suicidal plan of action so ruthless his superiors would believe him unfit for leadership. In the film it appears that Ender is simply trying to win the game as best he can. As for the Formics themselves, they operate with a hive mind so in a sense, yes they were all "involved" in the invasion of earth. However, wiping out of the entire civilization in retribution, especially once the audience hears the Formic queen express her dismay over the Formic's actions, is evil. The film somewhat glosses over this fact, but in the books it is clear the Formics did not understand that humans were sentient at all because they could not comprehend an intelligent species lacking a shared consciousness.
BaconIsMyBFF
Yeah misunderstanding is the constant of the book series.
lionhead