Many years ago (maybe 2004) I read an article in Psychology Today.
If I recall correctly it wasn't even specifically about terrorism; it was about how there can be things that are unpopular to say but need to be said, like talking about why so many terrorists were Muslim, except there were specific things about that.
Most of the 9-11 hijackers were from Saudi Arabia. Yes, it is a Sunni Muslim country, but it is also one with widespread income inequality and one that allows men to have multiple wives, greatly reducing the chance that a poor young man will be able to marry.
So you could worry that talking about that could increase religious prejudice or cultural prejudice, but you should just as easily be able to talk about how taking away positive opportunities for the young makes them more susceptible to negative influences.
(Also, any discussion on Saudi terrorists would need to get into the educational and news influences that their young men are subject to as well.)
At the time I took the polygamy factor as a testament to the value of marriage; that once a man has a home and family there can be enough validation and satisfaction within that nuclear family that it doesn't matter so much whether he is a leader at work or the alpha male of his friends or has some other way to dominate.
That could have been naive on my part. It could be that the wife and children are valuable as possessions and provide enough opportunity for domination. I don't like being so cynical, but there are reasons for it.
Terrorism and mass shootings are not exact synonyms. Terrorism would generally be expected to be political, and it doesn't require a gun. Mass shootings often don't seem obviously political. There are still a few things worth pointing out.
With the recent truck incident in New York, that does seem to be terrorism and he was radicalized here, in the United States. The September 11th attackers came here specifically to carry out their plan, but that isn't how things are happening now.
In addition, if you look into the backgrounds of the perpetrators of all of the mass shootings for the past several years as well as other acts of terrorism, the overarching common bond is a history of domestic violence. They have injured wives, children, stepchildren, partners, sometimes parents, but the violence started in their personal circle and spread outward.
Al-Qaeda put time and money and effort into carrying off their plan; ISIS just puts instructions out there for "lone wolves" who are looking for some way to have an impact. Maybe that matters, because September 11th delivered a bigger wound than, for example, the Pulse Nightclub shooting or the San Bernardino shooting. However, is that because it was bigger, or because we have just had so many other non-terrorist shootings that we can't even process them anymore?
We should be talking about things like that.