Humans are peaceful till their way of life is threatened. People with more resources will always be at peace, albeit to those who don't. Once the resources are depleted. No one would be talking peace, only fight to survive. Even today, countries fight each other for resources to make peace for themselves. Unless we miraculously achieve an infinite amount of resources for everyone. I don't think world peace is possible. 

It's sad to see such areas or countries still suffering because of war conflict. Yet I don't see big steps to end it soon. I think what is happening now is the same that happened throughout the history. Maybe it's culture's nature to be dominant over others. Sometimes war can be "cold war" such trying to be the most advance in technology or mideince. My point is the feel of satisfaction for countries to be dominated which let conflicts such war exist.

Is it appropriate to win better life by massacaring humanity?

I don't think so. 

 Being a vegan is the only way  . Only vegans refuse to massacre not only people but also non-human animals .