While it’s fashionable to argue that terrorists in Mumbai do not act out of religion, but are simply misguided, the fact of the matter is that they justify their actions in Islam. For the purposes of policy and security, religion should be what its practitioners believe it to be rather than what academics or outside commentators say it is. It is much more important to determine how terrorists are brainwashed in madrasas, then passing judgment on whether what they believe conforms to what academics believe Muslims should believe.
Along these lines, a few articles from the Middle East Quarterly archives looking at how radicals and terrorists justify their actions in Islam.
From a policy perspective, rather than argue after the fact whether these terrorists are justified in rooting their actions in Islam or whether more moderate Muslims take offense that terrorists interpret religion differently than they do, it is far more productive to recognize the logic by which they become convinced that terrorism is a blessed action.