I dunno, I'm not super convinced that the book promotes toleranceSpoiler:Here's an essay I was linked to on tumblr -
The novel repeatedly tells us that Ender is morally spotless; though he ultimately takes on guilt for the extermination of the alien buggers, his assuming this guilt is a gratuitous act. He is presented as a scapegoat for the acts of others. We are given to believe that the destruction Ender causes is not a result of his intentions; only the sacrifice he makes for others is. In this Card argues that the morality of an act is based solely on the intentions of the person acting.
The result is a character who exterminates an entire race and yet remains fundamentally innocent.
I think Ender's Game demonstrates how horrifying militarism and abuse are, and it asks us to condemn militarism and to empathize with childrens suffering, but I'm not sure the book exemplifies values of tolerance and compassion that might lead someone to reject bigotry. It's a cautionary tale of the dangers of xenophobia, but it also contains violent revenge fantasy.
When I think of fantasy that promotes compassion, I think of stories like Harry Potter. The Phantom Tollbooth, The Princess Bride, Paranorman, Star Trek, the Muppets, Dr. Seuss.
Superman promotes empathy and kind deeds. A Wrinkle in Time preaches love. Discworld mocks racism, sexism and classism. Terry Brooks' stories argue against suspicion, selfishness, war. Avatar the Last Airbender preaches nonviolence. In Pacific Rim empathy is used as a superpower, which through the plot device of the neural drift enables humans to defeat the aliens.
Series of Unfortunate Events - abused children demand accountability from adults and escape abuse by becoming autonomous and independent. They practice interdependence by maintaining caring sibling relationships with one another.
Ender's Game - abused children become heroes through channeling their pain and rage into violence.
Ender's Game is like a ghoulish nightmare version of Pacific Rim. The army creates soldiers by throwing teens into a pressure cooker, forcing them to bully each other, the strongest one defeats the aliens. I enjoyed the book but I don't think I'd recommend it to a kid, it's really grim.
The strongest warriors in Pacific Rim are those who respect one another and work together in friendship.
The strongest warriors in Ender's Game are those who are merciless.
It's a great portrayal of the madness and destructiveness of paranoid militaristic xenophobia. It's a great portrayal of how violence does deep damage to children. The characters tragically reenact the violence that they've suffered. But, I dunno. The heroes do not learn to solve problems with nonviolence. The characters learn to empathize with the aliens only after the aliens are destroyed. There's no kindness in the book.