Some atheists value intelligence above all else and feel the need to apply critical thought to believers reasoning (or lack thereof), and that application of critical thought is quite satisfying for to critique is to get an immediate sense of being right, by having shown someone else is wrong, whilst by one component of the definition of atheism is to deny theism and hence by applying critical thought in a negative manner some atheists can achieve that denial that is part of their belief structure.
Many people get a great deal of satisfaction from saying "NO you are wrong" with the obvious implication that they are right. Whilst the believer may discuss a concept that has many components in it, the atheist can point at any particular one of those many components and apply critical thought upon that one item and hence apply their denial strategy.
For about a year i've been having discussions with atheists on one particular site, not RF, and in not a single case has an atheist made mention of the points that were valid components of the main concept under discussion and have instead always attacked that one component that could fall easy prey to their mode of critical thought.
Some atheists will often, if not always, hold that the search for truth is achieved by revealing falsehood, this to my mind is fallacious reasoning a Denying the antecedent, or a fallacy fallacy.
Let me propose a question that may reveal the relative lack of worth in critiquing.
Which is easier for most people - to write a book, or to critique someone elses book?