An oft-made claim is that atheists are ignorant of this or that special reasoning about some religion and are therefore not in a position to lack belief in it.
Before even considering such special arguments that we're supposedly ignorant of, we must then ask 'What principle is being applied?' - for in the absence of some general principle, this is special pleading for ones own belief.
So is the principle something like all belief and disbelief must be fully informed, and without it, we must all suspend both out believing and disbelieving faculties? Surely not, for then no child could ever be indoctrinated with the religion of its parents, uninformed as it is. Advocates of such a principle must fight childhood indoctrination.
It's even worse - how many believers, even as adults - are even slightly informed about the arguments against the ordinary weak version of arguments that so many hold to? They are uninformed of those, just as they are uninformed of the 'sophisticated' arguments for belief that the apologists insist we must have, and the arguments in turn against those.
Is there are double standard, then, toward disbelief even though it is the the default position toward propositions until evidence or compelling argument is forthcoming? Such a double standard is of course, another form of special pleading, but let's see what happens if we for a moment allow it. Let's try to arrive at some principle and apply it only to disbelief in religious claims (allowing a first layer of special pleading for belief).
Then we have a principle something like 'you must know everything about any religious claim in order to lack belief in it', ignoring all arguments from the against side of the ledger.
But here of course, we run into the second problem - do believers apply that principle to beliefs other than their own? Do they know enough about other religions to reject them?
Overwhelmingly, and quite plainly not. Believers are almost entirely ignorant of even the basic beliefs of major religions, let alone the sophisticated arguments for other religions. Many don't do so well even on the doctrines of their own sects. Indeed, it's the atheists who tend to know about religious beliefs.
So a principle of even that kind isn't being applied to believers. We see a second double standard - a second form of special pleading.
This same idea pretty much applies to any argument that is made about needing sophisticated knowledge with respect to religion; they all come down to a form of special pleading.
When a theist calls for deep knowledge of their religion, they're merely making an argument from special pleading. Either the call is special pleading on its face, or it is based on a principle - but such principles end up at a double standard, for such principles are not applied to believers (and the people making the original argument assuredly don't want them to be), and so is special pleading at that point. It's special pleading, any which way you try to look at it.