MissBattleaxe re How is it appalling?
Well to me it sounds like he didn't fit in, the others teased him because to them he was ugly, I find that all a bit sad. Then he grew into a swan and realised he was beautiful, but he did not realise he was beautiful as that duckling. The phrase 'Ugly duckling' is sometimes used of children who are not attractive and grow into beautiful adults. That is all stuff I don't like as it is all judging by outward appearances.
But if you put it as "He was regarded as ugly and thought he had to change to be more like the people who found him ugly. In the end, it was clear that he was beautiful all along, he just didn't conform with someone else's view of beauty." well, yes and no, he was not 'attractive' as a suckling and that was sad. He ha to grow up to find out who he was.
I am not sure how you see it as "He wasn't ever ugly, he just didn't conform." Yes, that is true, of course, it was more that he stopped being a duckling. In the song that goes with the film the song goes...
'with feathers all stubby and brown'
I know I said I was commenting on the book not the film but the film is in my head! I was a small child at the end of the 60s so a lot of those old movies got in there how how!!
Yes, as you say "A bit of affirmation from people who accepted him for how he was born and boom! self acceptance." but not acceptance from the people who rejected him. I guess the social justice side of me wants the DUCKS to accept him. But yes, MissBattleaxe MAYBE How is it appalling? was a bit strong of me!