You forget wars. They're typically held over belief differences and conquest. Besides, I seriously doubt people going "Meh, don't give a damn." would stop some people from being complete shit.
Holy *whispers the "S" word to parents who don't give a shit*!!!!
I just remembered.
Muslim terrorists fight because of their religion.
Hitler faught because of race.
Stalin , and a few others faught because of conquest.
Because of all these genetic diseases and things humans get , someone might start killing people with genetic disadvantages.
Because of the amounts of unused land , people (like North Korea) will start wars for land.
It's rediculous what people fight over.
Lets all just be good to eachother , and we won't have no problems.