First off, they did keep the shower fight with Bonzo, though they toned it down considerably. No blood at all, if I remember correctly.

Secondly, you're spot on here. The central themes of the book are about the morality of total war and what that does to a person. The use of children as commanders and their "training" on the simulator provide a serious question regarding the accountability of people for their actions.

Roland00's claim that Ender is presented as "blameless" in this is laughably untrue; indeed, he is wracked by guilt throughout the book and is almost driven mad by the revelation that he committed xenocide. In the later books, his two drastically different personae are presented as separate entities in humanity's view: they cannot truly believe that the empathic and generous Speaker for the Dead and the vicious and violent Ender the Xenocide could possibly be the same person.