Atheism’s chief error is drawing conclusions too early in time. Most things will only be revealed and will make sense retrospectively (as the full work of God is not perfected yet).
Just because you haven’t met demons, doesn’t mean they don’t exist.
In “time”, all will know the Truth and when you’ve known the Truth, there’s nothing to deny and His Truth will set you free.
Most will learn the Truth and accept it only in the afterlife (may be long into the age to come before this happens) due to each one’s freewill choice of faith in this life.
You must understand a key thing when choosing what to believe:
“no matter what you believe, it will not change the existent evil in the world which is beyond your control (e.g. Famine in Africa). Likewise, regardless of what you believe, you can help to feed the hungry (a little solution).”
Hence, “feeding the hungry” by an atheist does not prove atheism right any more than a Christian doing that very same act out of his beliefs.
So, Truth which is independent of circumstances alone is Absolute. That, we contest is the Truth of God and there’s no way of proving it except knowing Him personally which is the basis of Faith itself (fact).
Even to believe, you must be allowed by the Father Who knows the hearts of all men :
“Jesus answered and said to them, “Do not grumble among yourselves. “No one can come to Me unless the Father who sent Me draws him; and I will raise him up on the last day.” (John 6:43 – 44)
Also, you will only know Him if the Son of God chooses to reveal Him to you (as He too knows the hearts of all men before doing so):
“All things have been handed over to Me by My Father, and no one knows who the Son is except the Father, and who the Father is except the Son, and anyone to whom the Son wills to reveal Him.” (Luke 10:22)
Atheists don’t get to set the rules as to “what type of proof they require” any more than they get to decide at what speed does the earth is set to revolve. That is, you don’t call the shots. None of use can. Only God does ultimately. A simple fact.
Finally, all creation will learn the Truth that “our opinions” didn’t matter at all; only “God’s Will” mattered in the “end” of “all things”.