Board Thread:Manga/@comment-26932251-20160922215635

Think back to Erwin's conversation with Zackly about the guilt that he feels for imperiling humankind for his own personal goals by overthrowing the government.

It's important to remember that nearly everyone really does believe that humankind will be extinct, the ultimate finality for all human beings and culture and condition, if the titans were to breech all of the walls and eat everyone.

That might seem quite a reprehensible thing to submit humankind's last remaining people to.

Except now we learned from Nile's monologue that Erwin was for a very long time skeptical of the assumption that humankind was extinct outside of the walls. And though he didn't advertise it, he almost certainly felt his assumption validated when he learned of the existence of titan shifters who came from beyond the wall. This is cause though they're originally in the anime referred to as "titan spies", he had to have reasonably concluded that they are human. So, fairly early in the main storyline, Erwin is able to reasonably assume with a large amount of certainty, but not total certainty cause he can't verify independently, that there are probably communities of humans outside of the walls.

It is still a dangerous action that he imperilled the human beings inside the walls (although I would argue also he gave the wall people their best chance of overall survival), but his guilt that he felt he could potentially be responsible for humanity's extinction was very misplaced as proven by chapter 85.

Zackly on the other hand is much worse because from everything we see, he does believe that the fall of the wall civilization represents the extinction of humankind but his own narrow minded ambitions are enough to make him apathetic to that. 