Let's assume our medical-minded would-be bombers were, in fact, motivated by religious ideology (or at least let's assume they themselves would so claim).
Let's also assume that maybe some of them were also "greedy" or egomaniacal or "lost, misguided souls" irrespective of any religious beliefs. Hell, let's even assume some could have been full-blown sociopaths...
It seems to me the crux of this discussion should be the question, "Without their religion, would these individuals have been as likely to attempt mass killings of innocent civilians?" I think the answer is "no" and I think Hitchens would agree.
Answering "no" to this is not the same as saying "Religion is the root of the problem." (I don't think we've established there is a clearly identified problem and that it has a root cause.)
Hitchens writes, "Still, the aberrant and the sadistic don't seem to explain the resort to murder in the present case.[...] So, we must look elsewhere for the explanation. Why have doctors apparently become killers in this instance? That's easy. Because of religion."
I find it hard to disagree with him here. It's tough to imagine that without their religion, i.e. their system of belief that (rightly or wrongly) informed them killing civilians was ok, that these doctors would have banded together and taken the actions they did.
Alt view suggests that crazy, violent individuals may use claimed religious conviction as a cover or a channel for their pre-existing sociopathic tendencies. While it seems certain that this must be true sometimes, this does not counter the argument that some religion legitimizes, encourages and facilitates acts of horrific violence.
It also doesn't address the issue that religion itself may have had a hand in creating these pre-existing tendencies. Crazy, violent individuals don't pop into the world fully formed. From what little I know about "religious education", certain varieties encourage children to grow into adults primed to suspect, hate and, if need be, kill outsiders.
Finally Alt view writes:
"If religion itself were to blame, wouldn’t more followers of a faith hold the same convictions and wouldn’t we all have been blown to smithereens by now?"
No - or more precisley, only if the religion in question clearly and absolutely mandated the smithereen-blowing.
But religions don't generally do this. Most Muslims don't think it's cool to kill innocent civilians. Most Christians don't think it's cool to shoot abortionists with sniper rifles. And most Jews don't think it's cool to machine-gun a crowd of Muslim worshippers.
But some do.
Most others of the same faith as the murderers don't murder. But this does not weaken the argument that religion ecouraged, justified, and facilitated the killings.
Looked at epidemiologically, belief in a supernatural being is a risk factor for large-scale violence. E.g., when I read that George W. Bush's religion teaches him about "end days" and the apocalypse, it makes me much more nervous than if he were just dim and extremely ill-informed.
Without benefit of his religion, Bush might well have invaded Afghanistan and Iraq - we'll never know. But the fact he believes he talks to God and thinks the "end days" may be near make it possible that in this case as well, religion could ultimately provide encouragement or justification for unheard-of destruction.
Similarly, it's hard to imagine the 9/11 hijackers doing what they did based only their perceived ill-treatment at the hands of the West, etc. It seems to me that a belief in an omnipotent and omniscient being was a prerequisite for the kind of willingness to kill and die they demonstrated that day.
FWIW. I'm not arguing that "religion is the root" of anything. I only state that in the current situation in the UK, I'd bet the failed bombers would not have organized themselves and done what they did, had they not first been convinced that God thinks blowing up British civilians is peachy-keen and they'd be richly rewarded in heaven for their efforts.