If you read the article, their (Pakistani Atheists) main concern is to not be killed. The Govt of Pakistan has blasphemy laws, was contemplating an Apostacy Act, and also thy fear for their lives from Muslim fundamentalists. From the article:
In 2007, the Islamist political parties of Pakistan tabled a bill in the parliament called the Apostasy Act 2006 that proposed death sentence and life imprisonment for male and female apostates, respectively. It was sent to the parliaments standing committee concerned for review.
They realise that they belong to a country where apostasy means inviting the risk of death even if spared by government authorities and courts, a fanatic mob would certainly not.
Maliha thinks that a confession of all-out atheism would cause an upheaval and says that she is not ready to face that yet. My parents are moderately religious and get upset enough at what they see as my growing heresy, she says. My best friend, however, is deeply religious, and, she has tried several times to bring me back to the right path, using a varied approach, including emotional and rhetorical arguments. I try my best to avoid the topic altogether with her, as I do with other religious friends - or else I listen to them, even while firmly, but gently resisting conversion. It is tough, not resisting the arguments themselves, but the emotional trauma and the sense of being so thoroughly alone is ones perception of the world.