"I understand how the damn Porter works perfectly well, and you're dooming the whole world."

Because the porter channels the energy from the breach in reality. That's one of the things the DO know, if he blows the Porter, then this is all going to go a lot worse.

"But by all means, destroy the world because you hate living."

The man is frustrating and David is close enough now to tackle him, but instead he swings with a blade. Why won't he just die.