I just watched that opeing bit again with Jacob & the man in black. Here's a key part:

Man = Still trying to prove me wrong, aren’t you?
Jacob = You are wrong.
Man = Am I? They come, fight, they destroy, they corrupt. It always ends the same.
Jacob = It only ends once. Anything that happens before that is just progress.

This totally sounds like God and Satan talking about humanity in the first chapter of Job. Satan basically says that humans love God because God is good to them but if bad things happened to them they would no longer love God. God says Satan is wrong. God accepted this wager, letting Satan do bad things to Job, to prove Satan wrong.

In the conversation with Jacob and the man, the man seems to be saying "Humanity sucks and is always evil." And Jacob is saying "Give them a chance, it's not over until it's over."