I think I'm going to piss you off, TrashMan, but first, I'd like to say that this isn't about you, it's about christianism in general.
That being said, I'm sure that people who call themselves christian would also be looking into the Old Testament, also in the Bible, which clearly state "an eye for an eye".
Welle, it isn't about christianism but more with religion in general and the hypocrisy which the people in charge generally show.
That being said, and to try to steer this topic into the original direction, I'm also of the opinion that the Shivans weren't really trying to wipe out the GTVA at Capella. If they really wanted that, the number of Sathanas present would have been more than enough to wipe out all the military facing them.
One of my pet theory is that the Shivan know that the race facing them know that the best way to counter them is to collapse the nodes that let them arrive. And this way, they could be protecting the other race from the true destroyer, who could be coming from subspace (or freespace, as it is also known and could explain the title), or simply be battling the Shivans in the same system the GTVA found the Shivans.