I'm probably not saying anything that hasn't been said already, but here goes.
Newgrounds is a gathering place for creative potential. We're designed for the purpose of collecting animations, games, and in the future (hopefully) art and literature, all to be shared openly, without fear of getting shot down by the FCC. The staff said it best: "When we say everything BY everyone, we don't necessarily mean everything FOR everyone."
And yes, a lot of the stuff submitted to the site is offensive, borderline offensive, violent, profane, perverse, adult-rated, or just plain crap. But we have a lot of great submissions too, some of which are perfectly fine for any audience. Newgrounds is a place for entertainment, and getting your name out as a creative talent.
As for the BBS, the people here really aren't any different from the people at your high school (unless you attend some private prep academy, in which case it's only mildly different). True, there are some ridiculous, obscene people here who think anything is funny if you pour enough semen on it. But there are intelligent people too, who can actually take the world seriously and still have a sense of humor about it. We make crude jokes, drug references, sarcastic empty threats; but for the most part we just want to have fun, and there's nothing you'll find here that you won't overhear in a middle school hallway (sad as it may be).
Nutshell: we're not dangerous, we're not problem children; we're just people with a place we like to go. And if you think Newgrounds is a bad influence, you should take a look at the real world.