http://en.wikipedia.org/wiki/Reductio_ad_Hitlerum
I like how you choose 2 extreme types of brutal peoples to prove your point.
Has spreading any religion reduced violence?
Your reply (as I expect to be) will be to say that civilizing the world was done with by the British and West Europe. So if we civilize does that make us more "good"?
Let's count the # of deaths inflicted by "civilized" societies (i.e. let's choose iraq because it's fairly recent and not a outdated example like 1940s nazi germany or wayyy back to aztec days, where in iraq over 500k people (very very conservative number i'm picking to give you benefit of doubt) have been killed). I thought the USA was "civilized" and civilization promotes good and pro-life. I guess not.
Now let's look at noncivilized people and their "skirmishes", where 1000s or 100,000s die at best...and to give you benefit of doubt, let's choose Rwanda, where semi-civilized people killed 500k (another estimate) people, using the weapons provided by civilized nations.
So I guess civilizing the world doesn't necessarily make it better.
The world is violent, either with a spear, gun, or button on a joystick while sitting in a air conditioned war room.
Religion has no affect on people's goodness and should never be confused to.
Good people are good, regardless of religious beliefs, or lack thereof. Bad people are good, religious or not.
These things are mutually exclusive, not inclusive.