Most of the un-religious persons do take something else as their religion.
Some pickup science as their religion.
For some, it's mother nature.
Others, nationalism/patriotism.
Or else, communism/equality.
There's always something that they treat as *their* religion and use it as a shield or weapon against others they deem as religious, while believing themselves as not.
Therefore the question isn't who's religious who's not.
The question is who has chosen what as his religion -- the age old question.