User blog comment:GethHaveFeelings2/VOTE: 11/@comment-1388547-20120823220709

For me, the hard decision would be to save or destroy the rachni queen. They almost conquered the galaxy before, and if the queen isn't on the up-and-up -- or even if she is, but her successors aren't -- they will have had the chance to learn from their mistakes and be even more effective this time. In the game, it's easy to be all morally superior and refuse to commit genocide even in the name of galactic security. In real life ... there are no do-overs. Without any way of knowing how it was going to turn out, I would have a hard time deciding whether to safeguard galactic security by killing her, or take a moral stand and let her go free.

(If the full threat of the Reapers were made clear by that point, it would be an easier decision -- save the rachni in the hopes they'll act in their own self-interest and ally against the Reapers, since if we don't stop the Reapers there won't be any point worrying about the rachni's long-term intentions.)