Would it be impolite to ask what kind of pirate doesn't rip off the dead?
End of quote
In the context of the original poster's message, I see it as bug exploitation. If a civ is listed as defeated, it should be dead then and there. The lingering around a turn longer happens because cleaning up the map and straightening out all the details doesn't happen immediately. It would be nice if this could be fixed so that diplomacy could immediately be cut with a "dead" power to plug the loophole.
In the vein of my character, on the other hand, my rules of engagement are pretty clear cut. If I have to fight to get a decent position or to respond to a sudden war, my fleet may well be big enough for an alpha strike right away (I tend to have stacks of transports and warships just lying around by mid-game ready to respond) but I will fight a limited war instead. I'll take out the starbases (to steal the resources and weaken the enemy), crunch a good portion of their fleet, and then take a few planets. It is then time to open up the peace negotiations and loot them. After that, the war is over and I will be content to culture flip them later.
If the war starts up again for some reason, I repeat the process for another limited war with a nice payoff at the end. Nothing like a victim that not only keeps on giving, but is foolish enough to attack me after I clearly have an advantage over them from the first time.
Eventually I might tire of dealing with a foe. For whatever reason, I decide that the promise of future payoffs is worth less than the problems they are causing. Then they are marked for death. There will be no negotiations or compromises after this point. The enemy will die no matter what I am being offered.
So I am the type of pirate who would prefer a cut of the profits while corrupting the alien culture, the old trade route and culture bomb combo. Outright warfare is kept to a minimum. All those warships sailing around shooting everything are bad for the freighters and my percentage of the take.