I don't think you're a troll. I'm not gonna flame you, maybe you're new here. Or maybe you're new to the realm of Fanfiction.
Either way, there are a few things wrong with your argument.
Stories that contain lemon and/or 'other inappropriate things' are marked accordingly for other people to read. And even then, not all under-thirteen people are here to read aforementioned fics.
Age restrictions are a hard thing to enforce anyway, because as everyone knows, "Everybody lies."
About the terrorist thing...Somehow I don't think terrorists are a big problem fan fiction-wise. And if we're going to ban terrorists, are we going to ban anarchists too?
As far as I know, 'Terrorist Blood' is not an existing medical condition. I'm not entirely sure where you get your facts from, but you might want to check your sources.
As far as quote-unquote "Good Writers" go, opinions vary from person to person. I think Stephen King is a genius and that Stephanie Meyer is a horrible author. However, somebody else might think the opposite, so there's really no barometer.
If you intend on only letting "Good Authors" on here, I strongly suggest you make some sort of test to factor where each writer stands. You're probably the only person who would care about all this, so you'd have to carry the test out yourself.
Really, think it through.