Frankly, Violence in the news is quite often just as bad as you get in the cinema or anywhere else and as far as nudity goes, if you haven't already got it then one day your very like to get a good insight into it or you're not actually interested in it (but normally before 18 you probably wont really know anyway yet).
I'm 18 and turned it off as soon as I could, I just got really irritated before because I missed so much amazing photography.
The problem with mature content filter on dA, is that it doesn't work well! I see a lot of really disgusting, and perverted porn photos marked to be non mature content, but on the other hand many deviations get mature content tag, that should not get them.
For example once I saw a photo of an animal eating another one. A beautiful shoot, straight out of National Geographic, and some smart ass reported it to be mature content, and after reviewing it, the dA staff agreed, and put a mature content tag on the photo.
Also there are so many-many amazing deviations which present the human body in a very-very artistic manner, and I don't think that under 18 they should not be seen... It wouldn't harm the kid, I'm sure!
So after all: if it's on you miss a lot, but still get to see porn and lot's of it. Conclusion: just switch it off, and if you are under 18: lie about it!
I don't get the sense of the mature content filter, I mean, your body is part of your life. And the filter is so strict, even in a swimming pool you see more skin then what rests unfiltered here. Have you ever been on holidays in Turkey, Côte d'Azur, etc.? Many women don't care if you see their breasts there. So why would you care? And when you get dressed in a swimming pool's changing room, how many naked men do you see? 10, maybe 15! Why should photos be censored, while real-life isn't at all? Thats what I think...