Think about this...
How many lives would have been saved if Ellie just stayed in Boston?
How many Hunters and Fireflies would still be alive if Ellie just stayed in Boston?
Poor David wouldn't have gotten is face sliced off if Ellie would have stayed in Boston.
How many lives would have been saved if David didn't like to eat humans?
He did what was necessary to survive.
Ellie didn't need to go across the country to survive.
Indeed. How could I not see that? David murdered and ate people to survive and help his people survive. He was a good man.