I hate to put it this way, but you are also not writing the story. Can you be so obtuse as to see that attacking would have killed Mikoto and summoned Gunnhildr and more people would have been tempered and now it was your fault? I'm sure Louisoix, who you are manipulating his words to fit your situation, would have had the same note of caution (rebelling against the norms of your culture for the greater good of the world is NOT equal to throwing lives away because you obstinately refuse to let your WOL have the personality trait of "caution").
Yes, it was the right choice. A hundred times over and over. The main force of the resistance wasn't tempered even if we lost "the squad," so the war effort can go on. Mikoto was saved so at least our friend and ally (who can see the future and has the echo and the scholarly knowledge to benefit the war effort) can live on to help. The first and second in command of Blades were also not lost, so the command structure for the resistance is still in place. I know it wasn't a perfect solution and we lost the Blades' elite squad, but you haven't been paying attention-- It's "For those we have lost. For those we can yet save." If the story hasn't taught you that you can't control everything but should persevere anyways and continue to see it as "ineptitude" then you have truly missed the point that this whole situation could have been far worse.