Your understanding of the "file sharing" world is rather incorrect.

The people who host the website are not originating the content -- people are, who do not "profit" as a fence would, they "profit" by having access to the things others share. The hosters of the website profit -- if they do at all, through advertising and donations by members -- and most of the time (though can't speak to this particular website) said "profits" are not profits at all, but are meant to share the burden of maintaining the infrastructure rather than anyone getting rich. This is not to say embezzling doesn't occur, which it does on occasion, but it's not the norm or intention.

Regardless, the people doing the work and reaping the benefits are not thieves or fences. At the lack of another word, they are "sharers" (excepting those few who do indeed profit off the enterprise). I say this not to try and play down their transgressions but to try and point out that they are a beast without another definition and to try to pigeonhole them as something they aren't (for example, fences, someone who attempts to profit on stolen goods). It is the same thing as showing your friends a copy of your book -- except that your friends are infinite and everyone can have copies at once. It's super sharing. This isn't something different so much as it highlights the flawed logical conclusion that "showing what you have to a friend is OK". A friend that borrows a book from my shelf and reads it in lieu of buying his own copy in the store is a lost sale for you, no different than someone who searches google on the way to Barnes and Noble and downloads it instead of buying it -- the only differences are:
1) We've all borrowed books for so long that it's ridiculous to think otherwise
2) First sale doctrine which makes this act explicitly legal (as in, it's not just "not illegal").
3) Technology allows us to do this on an exponential scale compared to simply lending out our books.

When someone paid for a book 20 years ago, they paid for the content of the book as well as for a service -- to have this book reproduced, packaged prettily, marketed so they'd know about it, etc. We live in a world now where the service of the publisher has been usurped -- technology has made it so their job can be done by teenagers in their moms basement in Ukraine so fast, and so cheap, that they don't even bother expecting money in return. This is a threat to publishers, not to creators. It is a joy for the writing community at large, because now there is no impediment to making your work available to anyone who wants to see it. For you, it's a threat to your livelihood the way you make it now, but not to its existence. You may have to figure out how to make money differently. You may have to deal with making less. But there will always be a market for good fiction, and if good fiction is what you make, then all you have to do is find it. Maybe you should spend your time opening a dialogue with your fans and figuring out how you can create a mutually beneficial arrangement (they receive your work, you receive compensation) rather than clustering a bunch into a group and calling them names.