Human nature, without fellowship with God, is ungodly. And human nature, without fellowship with each other, tends to the inhumane.
Sometimes I hear the objection that the Christian view of humanity is too dark. We dislike the idea that we struggle with our own natures, that there are intrinsic problems with our natures. That raises a lot of questions, not least of which is: what good could it possibly do to focus on that? We'll get there before the end of this post. But let's start here: Is that view unique to Christianity?
Another world religion
Do other religions see humanity as struggling against evil? Buddhism's quest for enlightenment implies that most of us spend our lives in the dark. The eightfold path includes (among other things) right intention and right action, implying that naturally our actions and intentions are not right. The other points of the eightfold path also show that we struggle to have the right understanding or view, right speech, and so forth for all the facets of ourselves.
Academics
Outside of religion we find the academic realm colliding with the same reality. History can be a general way to understand the human story, and is full of dark episodes. The same can be said of literature, where many stories show a struggle with either unjust opposition or, more humanly, with our own character flaws.
Psychology
In psychology there are different ways to understand our human condition. For example, Jungian psychology speaks of our shadow, or dark side. Evolutionary psychology places our behavior firmly within the animal realm, where "morality" may not even be a legitimate rubric to apply to humanity.
The point
We can look at the problem from any angle we wish; we are still looking at the problem.
It is tempting to avoid recognizing the dark, unenlightened, or shadowy parts of ourselves. Though the struggle is universal, is it humbling. But those are the two biggest gains from recognizing those parts of ourselves: humility, and universal fellowship. What good could it possibly do to wrestle with the reality of the darkness within us? On the other side of facing that unpleasant truth is a warmer regard for the human condition, a lessening of hostility, a growth of compassion. All the serious methods for understanding ourselves insist on facing the problem: without understanding that about ourselves, we still have that peculiar fatal flaw that hinders humility and fellowship. This kind of enlightenment prevents any pride in its attainment.