We might think it's straight forward enough like that... its not always.
I'm asking curious questions to understand the fuel behind the post. Is an athiest so because he "lacks belief in God"? Some, but hardly most. We are all fueled by something. It would be wrong to assume that all athiests are the same and think the same way, just like religious people.
My questions are designed out of curiosity (when I say that I'm curious). I have no hidden agendas, other than to understand a person's heart, desires, goals, visions, joy, and pain.
For instance, I don't believe that pink unicorns live on Neptune, but if I started making posts about why I don't believe or why other's shouldn't believe, etc. I am positive there would be a reason behind it:
Do I believe that those that believe in pink unicorns are dangerous? Am I trying to stop them from believing because of something they might say or do that I am opposed to? Am I uncomfortable with the idea? Am I scared that I might exist? Do I hope they exist, but really don't think they do? Do I believe they are illogical? Why do I spend my time trying to show people that they are illogical in specific idea of unicorn belief. Does the belief system challenge something else of mine? Or is it that I want people to have a full life? Do I think belief in Pink Unicorns prevents full life? Or... Why do I even care enough to help them think clearly?
These are the sort of questions that come up that I genuinely want to know - I just don't want to make assumptions.
The 'an atheist who has a reaction to a story which influences the beliefs and actions of millions of people around them, must not have that reaction out of concern over the validity of the application of those beliefs, but because the atheist secretly also believes it. Otherwise they would also react towards other things like pink unicorns, even though nobody seriously believes in pink unicorns or applies beliefs about pink unicorns to the world around them thus cannot even be approaching a similar priority' sounds an awful lot like pushing a familiar agenda to me.
Concern for others and themselves, since Christianity and its tenets effect them and their kin more than tenets about a pink unicorn ever will.
The familiar agenda is trying to get an atheist to either convert by accusing them that they are not, in fact, atheists, or that if they are atheists they should be silent about Christianity because why should they care?