How we cite our quotes: (Chapter.Paragraph)
Quote #1
He did not believe that there was any biological form, however strange, which he could not accept in time and, perhaps, even find beautiful. The mind, not the body, was all that mattered. (3.9)
The quote ties in the themes of appearance and morality. As we said in our discussion of morality elsewhere in this section, the basis of morals in Childhood's End is reason. And reason says appearance is not important, but rather how a person, alien, or whatever, thinks.
Quote #2
It would probably be true in your case, but you must remember that most of the world is still uneducated by any reasonable standards, and is riddled with prejudices and superstitions that may take decades to eradicate. (4.59)
But that whole education thing takes time; it's not something that happens over night. Although given the history of humanity and racism—or is that speciesism?—we'd say fifty years is a generous timeline.
Quote #3
"[…]: the men of that age will be more stable than their grandfathers. We will always have been part of their lives, and when they meet us we will not seem so—strange—as we would do to you." (4.129)
The novel suggests that learning to look past appearances is really just making knowledge about appearances commonplace. The more you're around something, the less odd it feels.