However, childlike behavior isn't childish behavior. Childlike acts are one of wonder, curiosity, and, yes, honesty. They observe the world as it is, envision what it can be, and thus able to make it better. When one thinks about it, isn't this quite an ideal way of approaching the world? No parent teaches his or her child to bend and break to the everyday -- that child is taught to be stronger whether through hardship or success.
People might say, "It's impossible to be honest in the real world!" Yes sometimes being dishonest benefits others and hurts no one. For example, telling a white lie about someone's progress for encouragement or a flat out lie to protect a political dissident.
Sun Tzu has examples of spying and deception in The Art of War to thwart the enemy's strategies, not only to protect his own nation but to end the war quickly and prevent further bloodshed on the other side as well. He wanted to take All-Under-Heaven intact. That is why he says to treat the enemy soldiers well. That is why he says to leave an outlet even when complete annihilation of the enemy is possible. Sun Tzu is being idealistic here, and is doing so in the real world. What he lost is small. What he gained is historic.