Ender's Game Lesson Plan

Why did the I.F. need Ender to destroy the bugger home-world for them?

The novel says many times that the I.F. needed a brilliant strategic commander, someone who could out-think a hive mind. Moreover, though, they needed someone sufficiently brainwashed and vulnerable, who could 'push the button' in order to commit species-wide genocide. Consider how Ender's young age changes how he might be perceived by media and historians, and how it makes him vulnerable to manipulation and brainwashing. The dilemma of whether or not Ender is ethically culpable for genocide would be entirely removed if an adult with full awareness of what they were doing blew up the bugger...