If all you want to know is "Why a game, and why Facebook?" you'll have to ask the organization's founder, Mallika Dutt:
Human rights have to begin at home, and we really feel the best way to reach people at home is through the power of pop culture, which is what distinguishes us from other social groups. [...]
There's a lot of literature out there right now about how gaming has the potential to be a transformative experience. We've always been looking at what's trending, what's changing, and where young people are, and try to connect to them that way. Right now the answers are games and Facebook.