[When he speaks again he's a lot less angry. Marty has a point; neither of them can really claim the moral high ground here.]

Don't you think we fucking tried to find another way?

We had the finest minds on the planet look over the manuscripts and texts and it always came back to the same thing...People had to die for our sin's and our continued existence.

It's one of the earliest of life's lessons kid...good things always come with a price.