Peter van Inwagen is a leading freewill theist. In his book on The Problem of Evil (Oxford, 2006), he presents a theistic evolutionary version of original sin (85ff.). I'll quote some statements, then comment on them:
Natural evil, according to the expanded free-will defense, is a special case of evil that is caused by the abuse of free will; the fact that humans are subject to destruction by earthquakes is a consequence of an aboriginal abuse of freewill (90).
As regards physical suffering and untimely death, rebelling against God is like disregarding a clearly worded notice, climbing a fence, and wandering about in a mine field. If someone does that, it's very close to a dead certainty that sooner or later something very bad will happen to him. But whether it's sooner or later, when and where it happens, may well be a matter of chance. In separating ourselves from God, we have become, as I said, the playthings of chance (103).
i) I think there's an element of truth to this. Although I think some natural evils are second-order consequences of sin, I don't attribute all natural evils to the Fall. Rather, I think the Fall removes the providential protection from natural evils that humans would otherwise enjoy.
ii) As a Calvinist, I don't think anything happens by chance. That said, Inwagen's position is problematic on freewill theist grounds:
iii) Regarding the metaphor of someone who disregards a warning sign, the problem with that comparison is that it's too individualistic. If, indeed, everyone suffered because each of them disregarded the warning sign, then Inwagen's illustration would be apt. However, Inwagen is moving within a framework where some humans innocently suffer as a result of what other humans did wrong. Everyone doesn't climb over the fence. Rather, many humans are born within the fenced-in minefield. It's not about getting in, but getting out.
And the notion of collective punishment is problematic for freewill theism. How is it fair to suffer for the misdeeds of someone else? I should only suffer the consequences of my own free choices. I should not be made to suffer the consequences of someone else's misguided decisions.
Put another way, if a freewill theist grants the justice of collective punishment, then it's much harder to see how he can attack Calvinism.
iv) It also depends on who climbs over the fence. If an inquisitive 10-year-old boy climbs scales the fence, we don't normally think he deserves whatever he gets. We make every effort to rescue him before he steps on a land mine. So are we comparing the fence-jumper to an adult or a child?
In my experience, freewill theists typically compare humans to children in relation to God.
v) Finally, it's arguable that disclaimers like "use or enter at your own risk" aren't necessarily exculpatory. If an adult disregards the warning, he's responsible for his own actions. That, however, doesn't mean the person who created the hazard is therefore off the hook.
Take human hunting. Suppose an enterprising businessman creates a hunting range in which men pay to hunt one another. Say these are big game hunters who are bored with hunting animals. That's no longer a challenge. They wish to take it to the next level. The fact that it's voluntary hardly exonerates the businessman of wrongdoing.