I think that a lot of this can be put down to government. Given a title/authority/uniform with the weight of the state behind them, many people will behave in a way they never would as individuals as if leaving their moral compass at home when they go to work.
Thanks for sharing your thoughts and while I agree that a lot can be attributed to government especially in regards to the actual aggression being forced upon others, however it's the masses that are generally apathetic and they way outnumber those who are in government.
I believe that without governments persuading us that life is about competition for scarce resources, we wouldn't all be so suspicious of each other, we wouldn't be so inclined to shaft others for our own good and we might start cooperating instead of competing.
But maybe I'm just naive!