Good will spend ten years painstakingly building a farm, getting merchants to buy its stock, eking out a living from the land. Evil will pick up a rock, brain Good, and take its stuff. Then, of course, Good's half-dozen big burly neighbours of the MacGood clan will come along and beat Evil to death, leaving Good the ultimate victor.
If the Evils lurking in the wilderness get together for mutual aid (reasoning that the MacGood clan can beat even the strongest lone Evil by ganging up on it), they're abandoning their evil and becoming another faction of Good. 'Cause there's nothing evil about helping someone else, at its basic level.
Survival of the fittest. And ten little guys with sticks will beat one big guy with a treetrunk.
I think about these things too much, of course.