Definitely this. A terrorist with an engineering/chemistry/biology degree/knowledge could do a lot of damage in todays society. It's not hard to imagine if you let your mind wander

(the explosive homemade uav into a stadium would be pretty bad, could fly in from anywhere)

I don't think he gets that security is probability based, consequence * _likelihood_, then you concentrate on the factors you can control like monitoring for people with intent, looking for known patterns, developing response plans, etc

Limiting the technology available is an exercise in futility, and has negative impacts on society to boot