I see this response a lot and just wanted to make a generalized, short post about it.
What would it be like if creationists asked biologists for evidence of evolution, and the biologists suddenly started looking all offended, saying "That's preposterous, I don't have to justify it?"
When we hold beliefs or make claims about what exists, we should be able to justify those beliefs/claims to a skeptic if we want to engage in a discussion about what is/can be true and what is/can be known. Therein is the key: of course we don't have to justify if we aren't in a discussion about what exists.
I can justify anything that I believe. I don't understand why it's a big deal to do so. Something about the extreme reluctance to do so on theists' part seems very telling to me. I know I haven't been making many friends by requesting justification and asking tough questions: I've been accused on more than one occasion of being a bully, a know-it-all, etc. But I also have to ask why it is people are getting so defensive over what should be an easy question?
Well I can't speak on behalf of every theist out there, but I'll give a couple of my own reasons.
Firstly, If I justify belief from a pragmatic viewpoint, I can almost guarantee the response will be "but that doesn't mean it exists!" which is accurate, but defeats the point of pragmatism.
If I say that I only believe in deities that I've seen or heard myself, the usual response is that I'm either lying or delusional. That pretty much ends the argument, since I have no way to disprove that conclusion over an internet forum.
If I say that my prayers are more often answered than not, somebody will say that this is simply confirmation bias. Again, I accept that it
could be, but I have no way to prove it either way.
If I explain that for the most part I consider magic to be applied psychology the immediate reaction is that I have no reason to call it magic. I suspect the people who make this claim don't understand the point of psychodrama.
If I explain that my concept of the "ultimate god" is pantheistic, I'm again told that I have no reason to call existence god. When I explain the psychological gratification in doing this, people will call it a "crutch" or make it out to be a weakness.
Perhaps the main reason I don't look to justify my beliefs though is that I'm bored of doing so. My beliefs are unusual and require a fair bit of explanation. Keep repeating the same story for long enough and it starts to wear you down.
Don't get me wrong, Meow Mix, I like you and I appreciate that you are genuinely inquisitive, rather than simply looking to lay traps. However, when a theist says they don't have to justify themselves, more often than not, they're saying "I'm not going through all this again" rather than "I can't justify it".