Sweetie, that's just it. Your definition of "decent" isn't the same as everyone's definition of "decent." My mother's definition of "decent" is that everyone should worship god the exact same way, wear clothing that covers them from wrist to ankle, women should only wear skirts and never cut their hair and men should have super-short hair. That doesn't make that the correct definition of "decent." Same with people who think tattoos--all tattoos--and piercings are "indecent." No, it doesn't work that way.

If someone makes porn and then forwards it to you to be mean, then yeah, that person's being a dickweed. It's the act of deliberately trying to upset you that might give you a leg to stand on (though worth remembering that internet culture works just like any folktale--people are always waiting to see anyone with too high an opinion of themselves get taken down a peg). But the act of creating it? Sharing it with fellow fans? No. There's nothing inherently indecent about that, insofar as your feelings are concerned. In fact, it's pretty unfair of you to act like you have the right to control what people say, do, or create.

Yes, that includes what they say, do, or create with your characters. If you want them to stay pristine and perfect and pure, then the only thing you can do is never ever let another human being read your story. People think.