So to put the views of Jacob and the MIB in a simple terms as possible, Jacob believes humanity is inherently good and the MIB believes humanity is inherently evil, corrupt, and flawed. Jacob brings these apparently "inherently good" people to the Island to test whether or not they can discern good vs. evil, as shown in his conversation with Richard in "Ab Aeterno." Even though these people continue to die, Jacob still brings group after group to the Island. Different "experiments" that we've seen so far are the Black Rock, The US Army, The DHARMA Initiative, The French science team, and Oceanic Flight 815. Every experiment has failed. The Black Rock crew members were all murdered by the Man in Black, The US Army installed a hydrogen bomb they intended to test on the Island, the Dharma Initiative couldn't peacefully coexist with the Others, The French Science Team were all murdered by Danielle, and Oceanic Flight 815 couldn't coexist with the Others and only 5 original passengers (out of 324) are still alive on the Island. (Jack, Claire, Kate, Hurley, Sawyer). The Man in Black claims that all of these failures are due to man being corrupt, and will always choose evil over good when confronted with the difficult and dangerous situations that present themselves on the Island. So whose view on humanity is right, and whose is wrong?
I'm going to be bold and say neither is right. Here's a quote from episode 3 of Season 1, Tabula Rasa:
"I don't want to know. It doesn't matter, Kate, who we were - what we did before this, before the crash. It doesn't really—3 days ago we all died. We should all be able to start over." -Jack
And another one from Ab Aeterno, episode 9 of Season 6.
JACOB: Because I wanted them to help themselves. To know the difference between right and wrong without me having to tell them. It's all meaningless if I have to force them to do anything. Why should I have to step in? RICHARD: If you don't, he will.
These quotes show that man is not inherently good or bad, they are inherently blank, which is one the main ideas posited by philosopher John Locke. Locke came up with this idea as saying humans are a blank slate at birth. But these people coming to the Island experience a sort of rebirth. Their lives pre-Island don't matter anymore, they are a blank slate and can make any decision once they reach the Island. Jacob believes that his people will innately make the right decision, while the Man in Black doesn't. The actions of many of the survivors on the Island throughout the years seem to support the Man in Black's viewpoint, but it is important to remember that they are often influenced by what may be the epitome of evil-The Man in Black himself. Many people, when brought to the Island, are also negatively influenced by the power and mystique that is present on the Island. The DHARMA Initiative was particularly guilty of this. They thought they could gain an immense amount of power by drilling into the Swan pocket of electromagnetism, but only caused a catastrophic incident that was part of their decline on the Island. Mother told Jacob and the MIB that man is intrigued by the power of the Source, and wants to obtain as much of it as possible. But honestly, if you came across a glowing cave of light, would you try to go into it and see what it's all about? You wouldn't because you're inherently bad, but because you're inherently curious.
So it is my view that the people Jacob brings to the Island aren't innately good or evil, but they swing in one direction due to the many influences on the Island. Most of them end up corrupt, because the Island is a place that can easily corrupt. And they usually end up corrupt because Jacob almost never steps in. This would be fine if the Man in Black didn't step in as well, but he does in almost every case, and people end up dead because of it. Just like Richard told Jacob, the Man in Black will always step in.
Also, sorry if this is an amateurish attempt at a philosophical blog post, but it's a thought I've had that I've wanted to post for a while.