I agree with his comments so far as they apply to actual terrorists (of any stripe, religious or non-religious) It is the slam job on religion in general to which I object.
I used 'cult' to describe a certain mentality, not to denote all those with whom I disagree, nor even all non-believers in a Supreme Being. While the word 'cult' may hold negative connotations for some, so would any other word I might have substituted for it. And it doesn't dispell the fact that, for some atheists and agnostics, the ideal of human reason serves as a God-substitute, ie., the attributes of omnipotence and omniscience commonly attributed to God are attributed (again, by some) to Reason, which they often spell with a capital 'R', as if to deify it. In this way, atheism can function as a de facto religion. The essence of religion is not a belief in a God or gods, for many people belief in God but practice no religion, while Buddhism, one of the great world religions, does not believe in any God or gods. The essence of religion is a reverential attitude toward some supreme ideal. Thus the 'cult of Reason' qualifies.
Finally, atheism makes a positive assertion about God, namely that He does not exist. It is agnosticism which makes no claim one way or the other concerning God's existence. In fact, there are many Christians who describe themselves as agnostics, since they don't know, in purely rational terms, that God exists, yet they have faith, an unyiedling inner certainty, in His existence. It is the atheist who declares positively that God does not exist.