"Having had considerable time to ponder your query, my answer has not changed."
This part is addressed in Silentium, in a way I find both disappointing and satisfactory. Both!

The Iso-Didact Narrates on page 314 of Silentium:
"Tell me, Chakas [Guilty Spark], if this were your choice, after all we have seen and survived...would you fire the rings?"
He does not respond. I don't know that I expected a response. It is a question asked by way of farewell. And much of his memory will be erased upon arrival at his new station in the name of compartmentalization, if ever the logic plague were to return. For a moment, I wonder if he will remember any of this at all.
Later on, Spark narrates: "Would I fire Halo, if it were my decision? Not my decision. It has been done, but the effects are out of sequence, smeared in time - ghostly."

So, he doesn't answer one way or another. Kind of annoying, but I don't blame him; it's a big bloody deal! Let someone else make the decision!