User blog comment:Miskos3/Fairy Tail Chapter 486: The Fourth Guest, Review/@comment-4507125-20160524082154/@comment-7418318-20160524112925

Literally the only reason why the war even started in the first place was because the pro-Human faction wanted to protect Humans. If they weren't on mankind's side, the war would never have started in the first place.

Killing all Dragons is benefitial to everyone other than the Dragons themselves you say? Face. Sure Acnologia couldn't have known that this particular event would happen 400 years after he started his genocide, but it still proofs quite effectively that living Dragons can be quite benefitial to being other than Dragons, even without getting the circle of life, food-chain and balance of magic into the discussion.