A world religion would be impossible

That would not be sci-fic but fantasy instead.

Betrand Russell

I dislike and disagree with this idea.

The sole and most important difference between atheism and religion is that atheism is self-correcting. Atheism is the belief in what is rational, rather then what you have faith in. Essentially, the acceptance that we could be wrong, but we'd only believe it with sufficient evidence.

I, unlike some, do not hate religion. I honestly couldn't care about your views either way as long as you don't do something that I would qualify as immoral (all too often, act against your religion, examples being not killing gays).

Do agree that fantasy is sub-genre of science fiction?

No. While the words might allude to something like it, the actual meanings as used in society do not seem as similar to me.

What does this refer to?

There are some border line cases and there are some overlap but on the whole I do not agree that fantasy is a sub-genre of science fiction as fantasy is for the most part very very weak on the science part of the title science fiction.

The best border line case I can think of is the book "Too many Magicains" by Randrell Garrett where there exist a well work out technology of Magic in a similar world line to ours.

Heinlein did similar works also but on the whole fantasy is not a sub-genre of science fiction in my opinion but stand alone.

I love the stories of S. King but I do not consider him a science fiction writer.