focusing on the consequences, it would be a very difficult earth to live on if a a response (the gp's point) was that using violence/punishment/retribution to stop further aggression was rational. I agreed that in the context of pure overwhelming aggression it might be possible (ender's game), but I doubt we would have gotten very far as a species or a planet if everyone followed that mentality with each other.

The whole point of that book was that Ender was bred, taught and programmed to think that way and that it was wrong - it accomplished nothing. Even Ender himself realises this - and wouldn't have done it if he wasn't playing a game.