Hm. I honestly don't remember the part where Section 31 threatened genocide against the Andorians; my interpretation was that Section 31 was threatening to blow up Deep Space 9 to make sure that the Meta-Genome data didn't get leaked. Where did I miss this?
Well, I'm just wrapping up A Ceremony of Losses
and I know what he's talking about. It isn't that Section 31 said that they'd do that or threatened to do that. Sarina and Bashir are talking before they commit to taking the route that they do and Sarina suggests the lengths Section 31 may go to to protect their secrets. I'm not quite finished yet. I have about 40 pages to go but I don't think anyone other than Sarina suggests this.
The conversation takes place in chapter eight on page 79 or 80. She says
Just to be clear about my intent when I wrote that scene, it's possible that, in a moment of heightened anxiety, Sarina might have indulged in a *wee bit* of exaggeration on that last detail.