Presumably they mean that contextual advertising is hard to automate, thus requires consistent marginal human effort for each marginal amount of revenue. (Not sure that's
true, but it's what "scale" generally tends to mean.)
> presumably there are no advertisers (that we permit and condone) who would like to advertise terrorism related products?
How about a handgun ad (tagline: "When seconds count, the police are only minutes away.")? Assuming the advertisee isn't in a oppressive regime, you can make money by selling them guns (or ammo if they already have guns), and do some minor bit of good by increasing the chances that the next terrorist is shot dead before they can kill anyone. (If they are in a oppressive regime, you've at least added one more bit of impetus toward violently overthrowing said regime, and hey, maybe they'll buy one of your guns on the black market.)
Edit: depending on the type of terrorist attack, you could probably advertise other emergency supplies like gas masks or fire extinguishers.