> we are all humans, we should not continue to wage war against each other for any reason
That is easy to say when you have everything you need. People whose grandfather's land was stolen have no other recourse than to wage war against the occupation.
Even if they don't own it, should they not still fight for it? Is it not their right to murder the descendants of those who live on the land that their grandfathers once lived on?
Let us assume that I live in a country that your grandfather fled. Now you want to move to that country but the government will not give you citizenship. Nor did your grandfather not your father not yourself receive citizenship of the new country you are in, and you were even born in that new country (like your father before you).
What options do you have other than infiltrating my country and killing me?
Wars are never waged just to wage wars, they are a means to an end: territory expansion, access to resources, religious reasons, whatever. It’s nonsensical to say humans should wage more or less wars. I get wars are unpleasant and cause suffering. Shooting someone in self defense is unpleasant and causes suffering too. But sometimes it happens to be the right thing to do.