What primarily seems to motivate atheists isn't rationalism but anger – anger that the world isn't perfect, that someone forced them to go to church as children, that the Bible contains apparent contradictions, that human beings can be hypocrites and commit crimes in the name of faith. The vitriol is extraordinary. Hitchens thinks that 'religion spoils everything'. Dawkins contends that raising one's offspring in one's religion constitutes child abuse. Harris argues that it 'may be ethical to kill people' on the basis of their beliefs. The perennial atheist litigant Michael Newdow sued (unsuccessfully) to bar President Obama from uttering the words 'so help me God' when he took his oath of office.
This is clearly not true about philosophical atheists, but Ms. Allen is quite right about Dawkins, Hitchens and co. And almost all blog-comment atheists.