Scott,
That is an interesting opinion. If they are liberal, I would say they wouldn't be against security, but I think there would be varying discussions about the correct level of security.
I think that most organizations, and people in general, don' t think bad things will happen within 100 yards of them. When it does happen, they are dumbstruck and you will usually hear them say things like, "I can't believe this happened."
In this situation, perhaps they believed it couldn't happen twice. I think there was no way to stop this from happening, short of intervention from somone who knew about the plan.
In spite of bad things happening all the time, like vandalism, rape, burglary, child abuse, most churches refuse to consider the thought of anything like a security plan.
When people admit the need for security, they are admitting the world is a scary place. It is much easier to pretend bad things won't happen to you, but when it does, it is the stuff Post Traumatic Stress Disorder is made from.
G