Interesting that it is turning out to just not be true. This "conventional wisdom" just isn't. Turns out that when you kill them, they stay dead, they lose momentum and it becomes harder for them to recruit, not easier. The idea of some infinite wellspring of jihadists is just not the case. When your symbols are all killed, there's nobody left to motivate you.
Look at how pathetic the Palies are after Arafat.