In war, the civilians can't audit every move of the military. (It's impractical, both for reacting timely, and for keeping secrets from the enemy.)
If the military doesn't work with Google, they will work with someone else who might not put the same amount of pressure on the military about the practical limits on AI. Or, even worse, our enemy might use a significantly better AI that we do.
My hope is that "war" shifts to AI vs AI, machine vs machine. Calling people who work on AI for wartime purposes immoral is fundamentally immoral when AI in war replaces the need for human casulties.