My God knows my limitations. He knows me more that i do. But God exercises us to increase our abilities to reduce our limitations. Atheist challenges can act as the resistance needed for a shallow faith to grow in knowledge and strength. Atheist kick a lot of fence sitting Christians off their fence either into disbelief or to greater faith and more solid belief.
Of course sold Christians can cause fence sitting atheists to move in one direction or another as well. So it works both ways. A half hearted Christian falls away and a seeking atheist embraces Jesus as Messiah.
So yes Atheists can act as the resistance needed to strengthen a Christians faith. Like a good weight training session. Sometimes painful but their is no gain without pain.
There is a good parrable i know. i will post it here.
Push Parabol
A man was sleeping at night in his cabin when suddenly his room filled
with light, and God appeared. The Lord told the man he had work for him to
do, and showed him a large rock in front of his cabin. The Lord explained
that the man was to push against the rock with all his might. So, this
the man did, day after day. For many years he toiled from sun up to sun
down, his shoulders set squarely against the cold, massive surface of the
unmoving rock, pushing with all of his might. Each night the man returned
to his cabin sore and worn out, feeling that his whole day had been spent in
vain.
Since the man was showing discouragement, the Adversary (satan) decided
to enter the picture by placing thoughts into the weary mind: "You have
been pushing against that rock for a long time, and it hasn't moved."
Thus, he gave the man the impression that the task was impossible and that
he was a failure. These thoughts discouraged and disheartened the man. satan said, "Why kill your self over this? Just put in your time, giving just the minimum effort; and that will be good enough."
That's what the weary man planned to do, but decided to make it a matter
of prayer and to take his troubled thoughts to the Lord. "Lord," he said,
"I have labored long and hard in your service, putting all my strength to
do that which you have asked. Yet, after all this time, I have not even
budged that rock by half a millimeter. What is wrong? Why am I failing?
The Lord responded compassionately, "My friend, when I asked you to serve
Me and you accepted, I told you that your task was to push against the
rock with all of your strength, which you have done. Never once did I
mention to you that I expected you to move it. Your task was to push. And now you,
with your strength spent, thinking that you have failed. But,
is that really so? Look at yourself. Your arms are strong and muscled, your
back is senewy and brown; your hands are callused from constant pressure,
your legs have become massive and hard. Through opposition you have grown much,
and your abilities now surpass that which you used to have. True, you
haven't moved the rock. But your calling was to be obedient and to push
exercise your faith and trust in My wisdom. That you have done.
Now I, my friend, will move the rock."
All Praise The Ancient Of Days