The irony of the "God is evil" franchise threads emanating from this forum, is that whatever the accusation of barbarity is, our society actually practices the same. I'll hit on two major ones.
There are different views on what this means, whether or not punishment is temporal, involves fire, endless black darkness, etc. Ethan made an interesting comment on it that I'd like to hear more of once he (hopefully) returns. But for now, we'll go with the common view that the after life extends eternally, either in the presence of God, or separated.
Our society understands justice. We understand that certain actions our society considers a threat to the well-being of others should be met with penalties that hopefully will deter the criminal from repeating the infraction again, and warn others against doing the same. So I don't think anyone should be too shocked to find the creator of the universe has a similar sense of justice. That infractions have consequences both in this dimension, and the next.
Should anyone deserve to be punished eternally?
Imagine if humans lived eternally on earth (And figured out a way to handle over-population). That the only way a human could die was by unnatural means (natural disaster, fatal accidents, murder, etc.). Other than that our bodies would just continue on. Our hearts would never stop beating.
What do you think the penalty for murder would be?
It might be relatively similar to how it is now, but probably more severe. If someone murders someone, they're not taking a life that was already physically dying.
They would have taken a life that would under normal circumstances, just continued on. Now that never-ending life has just come to an abrupt, and complete end, never to come back again. I think there would be less courtroom shenanigans, and far more scrutinizing to make sure the guilty are properly punished, and the innocent (falsely accused) set free. The obvious penalties would be execution, and quite possibly (eternal) life imprisonment. To some, the latter might be considered worse. The problem with temporary confinement in prison would be that no matter how long the sentence, once the incarcerated is set free, he has all of eternity to make up for time lost. To some, that might making killing someone they hate worth it. And as I stated, the idea behind punishment is not just aimed at the offender, but to everyone else as a hopeful preventative. So, is God at fault for implementing justice within His creation, seeing we do the same?
And.....it's not that much different in our temporal society. We still end the life of someone when implementing execution. And sentencing some people to life imprisonment, never to see civilian life again.
One of the common statements made in the various God is evil franchise threads is that God did something aweful for no reason at all (fill in the blank with accusation). And fauxlaw often points out that there was a reason. Which is true. No matter the allegation, there was always a reason. And a valid reason at that.
In every situation where God commanded the destruction of an entire nation as a for instance, there was plenty of warning ahead of time. We're talking in some cases centuries of warning. We're talking about nations that intended to wipe the Israelite nation off the face of the planet. If a nation has a nuclear bomb pointed right at us, leaving us with only 2 choices to either retaliate which unfortunately means killing women and children, or letting them kill all of us, what would be the better choice?