It's damn rare -- at least for me -- to fine an atheist who outgrew his belief in God/The Great Spirit/The Nouminos like he did with Santa Claus, the Easter Bunny, or the Tooth Fairy.
Those atheists are as militant in their beliefs as any hot-blooded jumped-up evangelical Protestant.
(That's the loud ones, at least: The ones you know are atheists and are damn sure of it.)
The emotional attachment is still there.
It reminds me of a quote from the book Love and Will, by Rollo May:
Hate is not the opposite of love; indifference is.