On his website, Arminian Perspectives, Ben Henshaw has a questions page at which he answers questions about Arminianism and Calvinism that visitors to his site pose in the comment section of the page. Here is a summarized question from a woman named Lori with an answer from Ben that has been added to by SEA..
Question: If all individuals unable to make a morally accountable choice for or against God go to Heaven and God does not want “robots” in Heaven and provides us with freewill, why would he deny this choice to stillborn children, young children who die before they understand such a choice, or to those mentally impaired individuals who cannot make such a choice?
Answer: The nature of your question is mostly speculative. The Bible just does not address much of what you want to know. I do think the Bible plainly teaches that we are free moral beings that God holds accountable for our choices. I also believe that the Bible makes it clear that God only holds those accountable for their actions that can properly be called to account, in accordance with His wisdom and justice, etc. So I agree with you that God does not hold small children or certain mentally challenged individuals accountable. Still, life is precious and man never has the right to end another life. Therefore, regardless of what we may think, God knows what He is doing and it is only up to Him to decide what is best for one of His creatures (with regards to whether they should continue living or not).Moreover, God created the world to work in a certain way, with free will and cause and effect, etc. As a result of sin, death entered the world, and things like children dying too young or too mentally impaired to make a morally accountable choice take place. But it would contradict God’s design plan for the world to prevent all these tragic consequences of the sinful use of free will. For more on this, see Brian Abasciano, “Answering the Problem of Evil from an Arminian Perspective.”
I think we need to leave such things to God’s wisdom and discretion. We are not in a place to make those decisions for God.
I also agree with you that God does not hold us morally accountable for Adam’s sin, though I do think that the corruption that results from that sin (and other factors) will eventually cause us to sin. This is why we need Christ and this is why God ultimately judges His creatures based on their response to His grace, which, unless continually resisted, will lead the person to the remedy (Christ). This is why we are ultimately judged for rejecting Christ. We will also be judged for all of our sins that could have been forgiven, had we not resisted God’s grace to our own self-destruction.