I was thinking similarly, but not quite the same. How many terrorist are engineers seems to be a backward question. Would a farmer be a terrorist, or have any value to a movement? Professional welder? Carpenter? So there are certain people that fit and certain people that don't from the perspective of the terrorist organization.
Further still, who is more likely to be dissatisfied with the current state of their Government/World? The farmer? The employed mason? Or the unemployed specialty engineer? Who is more likely to notice corruption, the higher educated engineer or the lower educated restaurant cook?
In other words, I kind of agree with the premise that more engineers would be terrorists. I don't think that it's really surprising just by glancing at the world. I don't intend this as insulting, but the more intelligent people I know tend to be the most dissatisfied with our Government and the direction it's going. They tend to not hope on the band wagons, follow trendy music and fads, etc... The founders of the US were similarly well educated people who were fed up with their current government and figured out a way to revolt.