Chris Sullivan has an excellent blog on terrorist motives. Among other observations, he wonders why certain Muslims in certain regions (like Saudi Arabia) display such hostility while vast numbers of others in other regions do not (as in India and Indonesia and Pakistan).
A theory, such as Romney's and Santorum's, should explain, and a better theory should do a more thorough, logical, penetrating, and consistent job of explaining. For example, the theory that terrorists arise from impoverished people has been entirely discredited. The fact is that many are highly educated and not poverty-stricken. The theory that terrorists are psychotic similarly has no explanatory power. Why should there be a concentration of psychotic suicide bombers among Palestinians? Besides, there is no direct evidence that this is the case.
And so it goes. It's a shame to see such superficiality among presidential candidates. They lack understanding. One cannot expect their policies or judgment to be sound, assuming they believe what they are saying.