Yes, I’m on one side, with dictionaries, etymology, and the majority of atheists, and you’re on the other side. I would agree with you but then we’d both be wrong.

Google:

noun: atheism. disbelief or lack of belief in the existence of God or gods.

Gnostic - adjective. relating to knowledge, especially esoteric mystical knowledge.

Me:

Theism is belief in a god, atheism is a lack of belief. Atheism is not necessarily a belief that god does not exist.

Gnostic is about knowledge and not belief