it has a high potential for destruction that can’t be ignored.
I agree about that part, but only from a modern human’s perspective. We don’t have interstellar spaceships (even intrastellar travel is still a huge feat for humanity as a collective) so if such a spaceship from an alien civilization arrives here tomorrow, even if it’s a civilian one that was never intended to be a weapon - its operators could still cause us tremendous damage if they decide to use its power against us.
But let’s go back to cars. If you take a regular car to a small village of some lost tribe completely detached from civilization (for the sake of the argument, let’s assume that the ground is flat enough and solid enough to drive), you could probably use it to destroy the village. Take the same car to a modern city - and while you can still cause damage with it, it wouldn’t be as devastating since they know how to deal with cars and have the infrastructures and rules to safely deal with them. Bring a tank, however, and it’d be a different story.
I imagine a type 3 civilization would know how to deal with interstellar vehicles. Bring such a spaceship to one of its outposts - and it won’t be considered a weapon. Unless, of course, it happens to be one that’s actually designed to be a weapon.