It seems that every time a question like this comes up, I say "it's a matter of opinion" and leave it at that, which I'm tempted to do here: 'Radicals' will always consider those more hesitant to be 'conservatives', and vice-versa. That said, it's an interesting topic. I don't actually know any crazy fans in real life, so I can't answer that one, but I can't say I'd actually mind being considered 'conservative'. Whether we are or not is the question. Hm...

I'd say that everyone who writes halfway decent fanfiction has to respect canon to some degree, otherwise it's blatent Sueism. Respect isn't the same as conservativeness, though; some of the best fanfics I've seen have gone out on quite a long limb, but they're still on the tree, so to speak - it sounds like you're talking about the sort of people who jump right off the canon-tree and go swinging around on jungle vines like Tarzan. It may well be that 'we' (and I'll use that term very broadly) are convservatives, and likely also in the minority, but given that about eighty percent of the fanfic floating around tends to be rubbish, who says it's a bad thing? If conservativeness generally results in good fanfic, I'll take up the banner with pride!

...Though that still doesn't answer your question, does it? I've gone off on a tangent. Really, I just don't know. But thanks for bringing up the topic, because it's fun to think about.

(I have to admit, I had a plotline somewhat like that planned out once. It was even for Star Wars, though I lost interest in the fandom long before it could get off the ground - thank goodness. Maybe this guy will do the same. Maybe not. Here's hoping.)

A darkside Obi-Wan could make for a very impressive goodfic, but I doubt he'd end up a Mary Tsu, and that planned ending point is ridiculously out-of-character. Obi-Wan is just too hands-on to be an Emperor or similar.

Unfortunately, there really is no cure. In the example you gave, the best argument I could come up with is that that version of Obi-Wan isn't Obi-Wan at all, and that people who want to read fiction about Obi-Wan are going to be rather disappointed - but that's a tenuous argument at best.

I encountered one of those this summer. In fact, I dated on of those this summer, until he revealed that he thinks that Eddiekins is the pinnacle of the male persona. And started talking about weddings.

But anyway. Yeah. His was a gigantic OC Twilight fic, with vampires so superpowered that they were ridiculous even for THOSE books.

I gave up on trying to convince him that this "older than the oldest" character of his was not, in fact, a believable character.