Don't Stop, Keep Walking because You Were Born to Make History

To understand how special this resentment is, well, you must realize Oberon isn't only a story character who fulfilled a role in the series inner logic. Oberon is also a meta-story character that criticizes readers' irresponsible consumerist nature to pick and discard stories as if they were worthless. That's why his last stand feels heroically tragic to anyone who reads it (and why Andersen understands exactly what he is in a metasense and is unable to mock or taunt him), although would have collapsed the life of the planet in the trappings of the fictional narrative. It is not because of the in-story implications, but the metastory ones. He was calling the readers out.

He was tired of the readers treating stories themselves did not have feelings to be cast down a pit and forgotten after they were used. He is this pit, this abyss, and would have engulfed all of us indiscriminately. All this theme was done metaphorically and literally through the in-universe comparison of the relationship between the lostbelt (fantasy) and panhistory (reality) instead of breaking the four-wall as many metafictions do. But it was obviously meta-fiction exploration. That's why Nasu called him special.

When he says flowers and insects, truths and lies, are a complementary relationship I think he really talking about the roles of readers and stories need of each other to exist. Between fantasy and reality. There is no reader without a story, and a tale has no worth and is 'dead' paper without a reader. Merlin stands not as a regular 'character' but his role, as he said in Babylonia, is not having a story of his own. More than Guda, Merlin represents the ultimate irresponsible, fickle reader. He is outside and untouchable, watching in, most of the time not interfering. His role is to observe and watch stories and moves on to the next one after they are done. So Oberon, who represents this fictional world, is the guide, the prince, of sorts (he is the embodiment of Britain, that fictional Britain that was real for a while) hides from his view. He denies being observed. He blocks this story. In my opinion, that is why he opposes him and why he doesn't want anything to do with him.