I think after reading this conversation between you two... I see a mismatch in perspective. I think the wider problem is that "knowing" as you talk about it is something that is internalised, i.e. truly coming from within whereas the other guy likens "knowing" to "knowledge". And by doing so what the religious and the atheists claim to "know" really are externalised ideas supplanted into them.

Religious people don't "know" everything because they did long meditation over it. It's because they were taught from childhood how things are. Likewise for the atheists, they've been taught a worldview and eventually subscribe to it fully. They both never really come to "knowing" as you understand it from deep inner work