The first episode, and part of this second episode, focused on the impact of the Overloads on Earthling science. The vastly superior tech of the aliens makes our science unnecessary and obsolete. The impact on religion is even more destructive.
Religion is more than unnecessary in light of the Overloads. Their presence here on Earth is incompatible with the very bases of most of our religions. Karellen says this quite clearly near the end, when he points out that we already knew that all of our religions, with their competing views of existence and the universe, could not be right. But now we see that none could be right.
This, by the way, could well happen as humans go out into the cosmos as encounter alien intelligences - we don't have to be invaded to come upon this challenge to religion. Some of the essays and stories in Touching the Face of the Cosmos: On the Intersection of Space Travel and Religion delve into this issue.
It was portrayed cogently and beautifully in Childhood' End last night. The ending was also powerful, when Karellen reveals why he prevented our leading human couple from having children. It was to save them the pain that would ensue.
Tonight we'll see exactly what he was alluding to. In the meantime, hats off to Charles Dance for his customarily superb performance, and to Childhood's End for now breaking some powerful new ground on television.
See also Childhood's End 1.1: Familiar Territory and Childhood's End 1.3: Literally