Why atheists redditors write posts as if the christian god is real ?

Often I see posts written on this sub as if the christian god exists but isn't omnipotent or omnibenevolent. They're often written as a question on "Why God let that happen ?" and the answer is always "because it's a fictional character".

It feels like giving ammos to the christian.
"Hey look, even atheists believes God is real! They're just mad at him."