system
Given the following post, respond as if you're commenting on Reddit:
human
[The Culture]A Mind has to chose between protecting a space habitat with a few billion Culture citizens on it, or destroying an attacking ship which has a universe simulation running with countless sentients in it. What does it do?

The attacker is doing the sort of thing the Culture frowns on, running a universe simulation on "full" accuracy.  So within it are a universe worth of sentients.  The Culture ship can't talk down the attackers or rescue the simulated sentients nor run.  The only option is to destroy the enemy ship in a way which will end the simulation, or, let it's own habitat be destroyed.


What should the Culture mind do?


Let's add another wrinkle.  The attack is apparently of a misunderstanding, alas, one which cannot be clarified or corrected in time.  Not only that but the attacker is "nice", morally clean, has no idea it is killing something sentient and will know what it has done so right after it inspects the wreckage.  It will never be a threat to anyone again when it realizes its mistake.
gpt
We have an empirical answer for this: they would destroy the ship.


Most Culture minds quietly mess around with what the call "Infinite Fun Space", aesthetically-pleasing simulated universes which often evolve life:

>This was the way the Minds spent their time. They imagined entirely new universes with altered physical laws, and played with them, lived in them and tinkered with them, sometimes setting up the conditions for life, sometimes just letting things run to see if it would arise spontaneously, sometimes arranging things so that life was impossible but other kinds and types of bizarrely fabulous complication were enabled.


It's not clear how Minds square this with their usual dislike of overly-detailed simulation - maybe they back up any sentients contained therein, or something. But we see Culture ships fighting each other in *Excession*, and they show no squeamishness whatsoever as long as their cause in the Real is just.