Freewill theists typically regard libertarian freedom as a precondition of moral responsibility. And many of them regard libertarian freedom as equivalent to counterfactual freedom. The ability to do otherwise (i.e. choose between alternate possibilities).
That, however, raises the specter of counterfactual culpability, including counterfactual damnation. If they think, for instance, that God ought to judge a benighted pagan not by what he actually believed, given his heathen surroundings, but by what he would have believed had he been raised in Christian surroundings, then that cuts both ways, does it not?
If God should save him had he responded favorably to the gospel, given the opportunity, then God should judge him, not merely for his actual misdeeds, but for his counterfactual misdeeds. For all the evil he would have wrought had the opportunity presented itself.
Of course, Reformed theism and freewill theism have different ways of grounding alternate possibilities. For now I’m just addressing the broader principle of whether it’s ever fair to judge someone, not merely in light of his actual history, but his alternate history.