I disagree. As nice as it would be, subreddits do not exist in isolation from one another and very often, trends and behavior set in one subreddit trickle to others. This was noticeable leading up to the removal of /r/fatpeoplehate et al, and it's noticable right now. The flamewar between the radical left and right flows onto almost all default subreddits, and it does drive overall quality down.
But there's a huge difference between strictly moderation the (default) subreddits in a fair, neutral or balanced way, and deleting whole subcommunities because they "spam" r/all. Maybe a better idea. Would be to delete r/all?!
