I would agree, however your stance rests on the assumption that existence contains the immaterial, and I do not agree with that. There is no such thing as immaterial in my eyes.
I maintain that reality contains the immaterial, not necessarily existence. Existence as a term forces us into a certain understanding of the world, which would not necessarily include Reality. I would agree that there is no such thing as the immaterial in your eyes, as your (and my!) eyes can only perceive the material. However, I have experienced certain.... unquantifiable things that are [currently] best expressed through spiritual terms. Maybe one day we'll discover exactly how the the brain works in its totality. Until then, it is reasonable for me to express my experiences in an immaterial fashion.