"Why does Deadpool know he's in a comic book universe?"
"Because his ridiculous healing factor gives him a uniquely heightened-yet-detached relationship to his body, allowing him to see it as a thing outside his own self; as his body is the sole source of input about his world this lets him perceive and understand his world in an equally heightened-yet-detached fashion, seeing it as equally separate."
OR
"Because the authors were so sure the Deadpool comic would be cancelled that they just did whatever nonsensical stuff they'd never be allowed to do in another series."

Well, yeah. If Choice A is, say, offensively racist (a group of sapient beings is predisposed to subservience) in context of the real world (this is a belief used to justify historical suffering), then no amount of Choice B's in-world justification (their god made them that way) will make it less so because the author had equal control over both and could have chosen to avoid the offensive Choice A by avoiding its causal Choice B.
But if the author's real-world intent is to call attention to and satirise the real-world belief, THAT will cast both choices in a different light.