Why does this have to be a fight at all? o.O

Because you're attacking a maxim: "There has been a continuous line of human civilization for twelve thousand years now, which is a pretty convincing argument that our better natures win out most of the time… which in turn makes the argument that most people are basically good." Your words:

The problem is, that "if" is pretty big. In fact, I'm not sure I buy it, or the "well, we're here, so we must be doing something right" reasoning behind it.

Who was talking about society?

I was. You were arguing with me. You were directly contradicting the statement that 'if society >12,000 years, then people = basically good' in as many words.

But while we're on the topic, if it takes a social construct to keep people in line, and they "go bad" when that construct (enforced via implied threat of violence, no less) fails... doesn't that strike you as argument against people being "basically good"?

Not sure what you're saying here. "it takes a social construct to keep people in line" is a tautology. "in line" is the social construct. People outside of society are an identity. You're essentially saying "it takes society to make society therefore society = bad."

The supporting evidence was a quote from one of the survivors admitting exactly as much to a reporter.

Anecdotal evidence with an n of 1 does not a trend make. It's not food for thought, it's irrelevant to the discussion for every reason listed above.

You seem unnecessarily grumpy today. Is that part of being "basically good" too? Something else I just "don't understand"? ;-)

You're elevating your hand-wavey gut feelings to the logical equivalent of scholarly evidence and arguing that they're comparable. You are further doing so in pursuit of casting aspersions on my conclusions. Essentially, you're saying "you're wrong because I think you're wrong."

That doesn't fly with anybody. Ever.