The Rating filter for "All Shows" could use some work.
Someone asked for suggestions for TV-PG rated anime, and I did a filter for that, and the first thing that showed up was "Afro Samurai" that show is about as far from TV-PG as they come. It does show that it is TV-MA if you mouse over it though. There were a bunch of TV-14 shows in the filtered results as well.
It's because of a bug. I'll need to investigate to be sure, but what I think is happening is that the extra videos, like trailers or interviews are being considered instead of just the official videos.
[Update] Yeah, it's that. I'm entering a bug. Thanks for reporting!