I dunno, even though we'd only been attacked once the film did a good enough job of detailing how scared humanity were of the Formics returning that I thought their actions made sense within that context, especially given we'd only just survived the first encounter.
Yes, humanity was scared. But the speech from Graff to Ender at the end made it plain it was a just in case scenario. "End all future fights", as the line from the movie goes.
In the book humanity was being pushed back to Earth by an implacable foe that refused all communication and was methodically exterminating every human colony it found. Under those circumstances there is great incentive to do ANYTHING to survive. That was the justification the IF used for their monstrous treatment of the children.
In the movie that massive pressure was just not there. I mean come on, the giant time constraint they were under was "Our fleet will be in position to exterminate the bugs soon, we really need to find a commander for it".
That is hardly a case for genocide. I actually don't blame the humans in the movie. They did have good reason to be frightened. I am simply annoyed that the people making the movie felt the need to muddy the waters by making Graff and the IF seem like they were going overboard without sufficient cause.
Just because it all turned out to be a misunderstanding by the Formics that led to the war doesnt mean you have to make humanity seem like warmongers for defending themselves in the only way they knew how.