I don't doubt at all that Jackson is a huge fanboy who has put a lot of thought and work into his adaptions.
I don't buy that he's a fan of Tolkien at all. If he respected the man's work, he wouldn't make alterations to the story with no other excuse than 'I like it this way better', which is pretty much all he's had to say on many points when asked in interviews and such. It doesn't sit right with me when someone claims to be a devoted fan of someone's work, but superior at the same time.
Or maybe some new, fresh adventure using the Middle Earth as a background?
I'd be okay with this, but if there was this much rage over a bad adaptation, imagine the hatred of anything new Jackson comes up with. Even if it's at least passable, the rage would boil oceans.
Honestly, I wouldn't have nearly as much problem with it. Tolkien wanted people to expand on his work, and deliberately wrote most of the mythology undetailed, so that others would have something to work with after him. He wanted it to be a cultural heritage in the same vein as Nordic myth or something, to bring the same uniting factor and enrichment as those did in the past, because he thought such a thing was lacking in the modern day. And he sort of succeeded. He's been the main inspiration for an entire genre of fiction. Just probably not how he expected.
So people writing original stories fitting within Tolkien's mythology would be great, I think. Just don't be stupid about it. Bend canon a bit here and there, but don't shatter it. Don't be excessive with tying-in popular characters and re-hashing the same sequences over and over to please the masses who just want more of the same. That's probably asking for too much, but in theory, as a rather purist Tolkien fan, I would be cool with it.