I haven't encountered this conversation with anyone yet but I know it's bound to happen sometime soon.
So we believe in the Bible and that everything in it is fact. So it is easy (or easier) to convince someone (such as a Protestant) that your argument is true, for example our God is the true God.
Now how do you convince someone who doesn't believe in our God (an atheist, a hindu etc) that God created the world or even that He exists without using the Bible.
They obviously won't take the Bible as valid because the religion is fake in their eyes right? It's like a Hindu pointing to their book trying to prove that we get reincarnated into cows because this one guy in their fake book did. We wouldn't believe them, so how would they believe us if most of our arguments come from the Bible?