1. We didn't start the war with the cabal. They did. 2. The fallen aren't evil, they are just ruthless cutthroat pirates. 3. If we don't kill the cabal on the dreanaught they would detonate a bomb they had planted wiping out the entire human race, ALL THE AWOKEN, the exo, EVERYONE IN THE TOWER AND LAST SAFE CITY AND ALL LIFE IN MOST OF THE GALAXY.