And in exchange you would have a whole bunch of people who would be less inhibited in what they did because they wouldn't feel they had to answer for it later.
The whole point is really moot to a discussion about someone who went and killed a bunch of people.
I've never understood how one can imagine billions of people abandoning their values and turning into killing, thieving, rape machines all from finding out that there will be no ultimate punishment/reward in the afterlife. Everyone's problems and responsibilities would be the same after the revelation as they were before it. Why wait, we have millions of non believers who should apparently be running wild since they're ultimately free of everlasting judgement from a divine authority.
Of course we don't see that and instead they have to answer for what they do now, in the societies we live in with the one life we know for certain that we have. It seems to me that anyone who poses this theory must see divine justice as the only motivator for not turning into crazy people, while ignoring all the other factors which contribute to it in a much more immediate and meaningful way.
And where is moral accountability or justice when you can simply repent and accept Jesus and be back in god's good graces. Or what about people who believe they have good reason, reason from God himself even, to do something immoral or wicked? I don't think that having second thoughts about being punished in the afterlife would even occur to them if they think they are doing God's work or something God approves of. People will find loopholes in anything to do whatever they want to do anyway if they want to do it bad enough, even the supposed objective moral framework of religion.
I would think a person would find social awareness/cooperation more important to their personal fulfillment and longevity in a single knowable life, than they would if that life was simply a rest stop you lingered at until it was your time time to be judged on how many good things you did and bad things you apologized for so you can then be sent to the paradise of everlasting life.