If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.
But there are certain ideas that will be downvoted and dismissed because people feel like they aren't useful to be talking about, like if God exists. I think OP was asking if it was a topic that fell under this category.
The problem with "does God exist" isn't about the fact that LW is atheist. It's that it's hard to say interesting things about the subject and provide a well argued case.
I don't expect to learn something new when I read another post about whether or not God exists. If someone knows the subject well enough to tell me something new, then there no problem with them writing a post to communicate that insight.