this certainly is a controversial issue.
understand one thing: everyone is biased towards something, including the AdComs.
Readers in the admission committee are humans and have humanly feelings. Sure, part of it has to do with luck...that perhaps the reader won the State's lottery that morning and is letting everyone into the school (not likely, but always a possibility). By writing on some controversial topics, you put yourself at risk of having your application read by a highly subjective person. Of course, you can probably spin your essay well on any topic if you can write well, but just make sure that you have plenty of people read it beforehand to see if they may feel offended by your writing. I think by stating that you're an atheist, it really should be fine. And I do think you may be crossing the line if you start bashing on someone else's religion and/or politics.
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