Nope, you have to shoot. I don't think there's any ruling for it other than the Space Combat section stating "Each player makes combat rolls." No "may".
That's why the Brotherhood flagship is better than people realize. It's ability is expensive and situational, but it's like a real nuke - the threat of using it gives you more negotiating power. Park it near and important system, or home planet, and just threaten to move it in.
Thanks for the response. 16.3 Capacity was the key.
Previous games have made me wary of assuming the rules follow logical flow that you know they should. I like finding the text in rules reference early before it becomes second hand and you've learned they broke with logic.