It’s not a religious argument.

It’s a subjective experience argument. As a conscious person, if someone tells me they don’t believe in consciousness, then I’m inclined to believe they have a reason for saying that. They must not be experiencing consciousness the same way I am.

Interestingly, a non-trivial number of people have no internal monologue (https://www.iflscience.com/people-with-no-internal-monologue...). It would be reasonable to assume the experiential side of consciousness is on a spectrum, with extreme edge cases on both ends. It’s not unreasonable to assume that some people are barely experiencing it, and some not at all. It would certainly explain to me (someone who experiences it quite intensely) why some would claim it doesn’t exist. Because for them, it might not.