Why do people not differentiate between those who believe in god, and those who claim he exists with as much certainty as any living person?

By reciting the rosary each day with care, a person can know with certainty God exists.

I wouldn't "believe in" Him if I had not met Him and developed an ongoing relationship and communication with Him, as have hundreds of millions of other intelligent people. The real question is - Why do otherwise intelligent people claim that someone known by millions of other people doesn't exist, just because they themselves have not yet met Him??

And where there's danger there is also great opportunity/human potential.

What's the difference if I believe in you or if I believe you exist?

You use of the lower-case "g" in "god" makes it clear that you do not differentiate either. Good luck with that.

Demonstrate how having reasoned certainty in the existence of God is "dangerous."

I think you might be trying to get at something else here, but the only difference I see is between the strength of the beliefs rather than any difference in what they actually are. And I don't think that's where the problem is. A person doesn't need to be certain to devote their life to the religion. They just need to believe that's what the religion requires while believing just enough to make that leap.

The word faith in the Bible is actually translated into the word “pistis”. Pistis basically means “certainty”. So when a person says they have faith they are saying they are 100 percent certain of God’s existence. Belief is not a guess

there is no need to, dear. they both believe in God.

GOD IS CAPPED WHEN IT IS THE TRINITY!! WE KNOW HE DOES EXIST SO FORGET COMPARISONS....U EITHER GET SAVED OR U DO NOT....PEOPLE WHO BELIEVE IN JESUS ARE NOT DANGEROUS...GROW UP AND LEARN DECENCY....GOD IS JUDGE NOT YOU!!