The greatest challenge to the atheist is the 'problem of evil'.
It is so great a challenge to the atheist's construction of the world that he (and if a woman, she) has to use it to attack Christian theism...as they conceive it.
Most Christians seem to fall in to the trap, alas. And a trap it is; but most atheists also fall into it because they can't think of what to do with their own problem of evil: that they can detect objective moral failure in a material world, in a world of evolution where all but the least unfit are annihilated and where random changes in the genome while the putative engine of change, are the source of misfitting, disease, disability and life's existential struggle, in every dimension. That's their world, but they don't seem to find it congenial.
Thus they use it to attack the Christian vision because, they claim, it doesn't solve the 'problem' which in their world cannot exist, because it is a world without objective moral content.
To carry off their attack on the Christian vision, they have to pretend it is other than it is. They have to attack a 'straw' vision.
So they create a straw-god, and then claim he is not doing his job, and fabricate a straw-Christianity, and claim that it is incoherent.
Most Christians seem to also not know their faith very well. Faith is confidence based on knowledge. Our current Christian culture is light on knowledge in too many circles, and lets our detractors define faith as some sort of phantasm.
Here what's they miss out in their straw-manning of God and our faith.
God is all powerful, all knowing and all loving....then they go to town with their God the beneficent puppet-master.
Christianity, they see, is about obeying the rules, about 'cow-towing' to a mean dictator who demands that we set aside our rationality (which he created, don't you know), and 'just believe' despite the 'evidence' as they see it of evil, which has no reality in their own construction of the world.
All pretty amusing in a pathetically forlorn way.
So, how do they 'straw-man' God.
The omit his critical 'attribute' God is holy. The atheist's god is made in the image of the atheist: how the atheist would like God to be: a sort of moralistic-therapeutic-deism with God as the failed absentee sugar-daddy in the sky.Sort of like
Stanley Crawford's Gascoyne who elusively runs his show without showing up.
They decline to understand that the faith of Christ is not to join a rule-club, but to join the opposition to evil, to be rescued from it in prospect of the main game, the new creation.
Oh, they also decline to know what evil is. Evil is the denial of God, it is living in 'not-Godness'.
We can only do this not because of some cute 'free-will' as though free will is a triviality, but as those who are able to fellowship with God we are also able to meaningfully dis-fellowship with him. Otherwise it was not fellowship in the first place and WE WOULD NOT BE ABLE TO ENJOY GOD FOREVER if we were not true persons (i.e. in God's image as he is a person).
The atheist's mission is to live in not-Godness while having God prevent us from experiencing living in not-Godness. Not possible. Its like wanting to enjoy marriage by remaining single (married bachelors can line up over there).
Christianity is about our relationship with God as being in his family: to ultimately enjoy him forever, to inherit all he has prepared for us, to rule with Christ for eternity. Rule here as God showed what 'rule' is like in Genesis 1 and then in the incarnation: to do what is very good for others.
It is also about understanding that not-Godness discontents us with life cut-off from him to prevent complacency about our state. Not-Godness started when our first parents (A&E chose the idolatry of seeking knowledge from the tree, and not from God. They wanted to strike out without God, and of course, reject God and you reject his credit line at the same time).
All I ask the atheist is two questions: how is their rejection of God helping to undo evil (the outworking of our rejection of God and absent re-birth), and having rejected God, why would the world want to experience his goodness? After all, everything the world's denizens do is to reject God while usually complaining at the results of that obstinate choice.
But of course, the nail in the coffin of their view: who told them there is evil?
By their construction of the world they should be puzzled that anyone can even notice that there is a disparity between 'good' and 'bad', because there is no value basis in it by which to make such judgements. All they have is relative subjective uncongeniality of circumstances. Big deal, but that's all evolution gets you.
However, there is a point of contact. We do experience a disjuncture between what we think should be and what is. This results from the disjuncture between the world we experience and the base reality of the way of God. We are in a bubble of 'anti-reality'. God is thus merciful to enter into this 'bubble' to preserve this 'bubble' and us in it so that we may turn to him and finally enjoy him forever in a renewed creation.