Any ideas on how to roll back the previous interesting moment for a campaign i accidentally ran against large group of folks
There's no "rollback" for the Activity Log (for any activity types). It's an append-only log until entries age out.
I know there's not really a rollback, but I'm just trying to figure out a way to at least wipe out the last entry in Interesting Moments. Is this even possible?
No, that would be a rollback.
You could add another IM that represents the cancellation of the last one, but using such measures in Smart Lists becomes complex (you have to compare "number of times").