Reddit's response about the actions they took against the subreddits (note: r/mildly interesting DID NOT encourage nsfw content and their suspensions and removal have been revoked by a diff admin)
It's only because they were default subs.
A while back one of the news subs (r/world news? ) got flooded with porn and basically switched to a random anime porn type of sub. That caused the population to migrate to r/anime_titties for all their news needs.
Now when it happens to a special sub though it's a problem?
lol, I witnessed that historical moment, essentially r/worldnews become a wild west where any post is acceptable, and it's all 50/50 NSFW, you either get a naked lady or a butthole, while r/anime_titties are the proper sub for world news..
It was /r/worldpolitics, with anime_titties being the actual world politics sub. Similar to how /r/trees is for weed, and /r/marijuana_enthusiests is for people discussing actual trees