I didn’t know that CFI forum was a atheist online community, is it?
Not strictly, no. But part of CFI is the Council for Secular Humanism, which among other things works to protect the rights of atheists, and publishes a lot from a generally atheist point of view.
Speaking generally, there is a close affiliation between scientific skepticism of the sort CSI fosters and atheism as well. Though they are not the same thing.