Just so Christians dont think we solely pick on them, let me make this clear. If ANYONE wants to understand why we view all polytheism and monotheism as myth a simple experiment can be done by the believer.

First, if it would make no sense that a human is capable of having 6 arms, why would it make sense to believe in a deity that does?

The believer merely has "faith" that the things that dont make sense dont have to make sense.

OK, so here is what you should do to ask yourself why you believe what you believe.

Take a copy of Harry Potter and a yellow highlighter. Every time you hit a sequence of words discribing the impossible, ask yourself why you rightfully reject it.

At the same time take your holy book and do the same thing. Highlight the claims that defy logic and ask yourself why you believe it as apposed to the same illogical things you rightfully accept as fiction.

Even take another holy book from another religion and do the same thing and ask yourself why you rightfully reject those claims and reject Harry Potter.

It is a simple experiment that should expose you to why we reject your claims as well as all others.

"If it sounds too good to be true"

If a multiple armed deity sounds fictional why would you be immune to the same trap others fall into?

The point is to demonstrate that belief in the supernatural is not based on a deity being real, but based on the human ego projecting itself on a fictional utopia. Everyone wants a hero to protect them.