I almost spit out my coffee I laughed so hard.
That's how the alliance markets itself, but that's not how everyone in the world, especially their potential adversaries, perceives it. And its potential adversaries have been saying so, publicly, for decades.
As I'm sure you understand, all military alliances, even if they start out defensive in nature, can easily become offensive in nature.
> if they feel threatened enough
Exactly, they felt threatened, because they did not and do not perceive NATO as a defensive alliance.
I highly recommend watching the videos I linked in my earlier comment.