That wasn’t in response to a threat – that was just
because we could. The threat had already been dealt with.
(Do you think the Brisker Rav didn’t know the Megillah?)
I don’t know what you mean with the rest of your post.
If the enemy wants to destroy us, they’re a physical threat.
If the enemy wants to destroy Yiddishkeit, though they may use physical force to that end, they’re a spiritual threat.
There is an appropriate response to each situation.