again, front end automation tools are commonly banned, along with the developers. the ban was surely because how the tool was interacting with their website, not that the tool was trying to help people unfollow pages or friends.
some parts, but I believe any comments done through automation are strictly limited.
the issue in this case seems to be the guy wrote a plugin that interacted with the front end, which, again, has always been strictly prohibited, and commonly results in bans from the platform.