But that does not mean that all engineering and hard-science types are more likely to become terrorists.
Right, but that's not what I said at all. Regardless of why there is a correlation between engineering education and terrorism, there is a correlation; whether you're equipping potential terrorists with the tools to commit terrorist acts, or somehow making non-terrorists more terroristic, the end result is the same.
It just means that if you take a random sampling of people and you test them for terrorist potential you will find that the technical ones will do better at it.
That's interesting; I hadn't heard that the same kind of study had been duplicated elsewhere. Do you have a source? Before I saw the study, I was struck by how many of the 9/11 hijackers had an engineering, compared to, e.g., American terrorists. (The Unabomber is the closest analogue, and his academic background was fairly abstract).
What I think is that if having an education will make them less susceptible to brainwashing.
And yet that effect is clearly counteracted by whatever else it is that makes engineers more likely to blow stuff up. If they're half as willing but ten times as able to commit terrorist acts, we still lose.