A Common Sense Defense of Original Sin

If you went up to a random person on the street and asked them "Is man naturally inclined to good, or to evil?" you would probably get some very interesting responses. Some would say "evil," and you would instantly be able to explain the Christian idea of Depravity very easily, it would then be a mere question of "why is that" or, "what is the solution"

More interestingly, and probably more common, would be the response that "man is naturally inclined to good." This response naturally begs the question "Then why is there so much evil in the world?" I would imagine (and I am sorta guessing at this point) that you would get one of two responses, either A. "We get corrupted by society" or B. "Just some turds in the gene pool"

Answer B, of course, leads to another interesting line of thinking. Perhaps when you asked about "Evil," thoughts of Hitler, and Musollini, and Mogadishu flashed in their mind, but they think those people and places were largely isolated instances, but that the majority of the world is largely evil-free. But what if the standard of "Evil" is much lower? What if a simple lie is "Evil"? What if we define pride as "Evil"?

A person may object to this notion, saying that those things largely don't matter, but then the question is begged "Why do naturally good people have these tiny flaws?" Hopefully no one but the most staunch relativists would make the arguments that theft, and lies, and other such things are not morally wrong, but that still leaves us with the question of why we do these things.

This, of course, leads to the original Answer A. "We get corrupted by society." To which I would have this to say: "Isn't society composed of individuals who are, according to your theory "naturally good"? so, if individually they are good shouldn't society be also "naturally good"?"
or go even further and say, "If we are corrupted by society, and society simply consists of individuals who were on earth a few years more than us, would it be fair to say that we inherited this corruption from the previous generation?" and, if this is so, "Would it then be fair to say that at some point in the past, some naturally good human would have had to "invent" or "stumble" upon evil, and pass it on generation to generation to us?" to which I would answer in the affirmative.

We call this man Adam