"But "delusion" goes beyond this. Dictionary: delusion: a "false persistent belief"

It therefore states that anybody who believes in God is dead wrong."

No it doesn't. Even Richard Dawkins says he is not certain that God doesn't exist. The delusion refers to the whole world of belief, with all its ceremony and trappings and elaborate "theology", that revolves around a being whose probability of existence is vanishingly small as measured on any rational scale.