So by calling for a “challenge” to the Saudis and Qataris, the archbishop is throwing down the gauntlet both to Salafism and the Brotherhood; he does not say which form of Islam he thinks should be encouraged instead, but “global mainstream Muslim leaders” sounds like a reference to products of the traditional theological schools of Egypt or Jordan which are conservative but not especially political or supportive of jihadism.
Some of the people who argue that terrorism in the name of Islam has a theological dimension (in other words, it reflects bad theology, which must be driven out by good theology) weaken their case by over-stating it. This exaggeration can be self-serving. Their implied message is that no other factors (social or economic woes, political or geopolitical grievances) are worth considering and that expert theologians, capable of correcting Islam’s current pathologies, are the kind of people that the world needs most.
But Archbishop Welby is not over-stating the case, he is simply stating it, rather obliquely and politely. And it is a case that needs to be stated.