To one who has faith, no explanation is necessary.

One of the ways to identify a bad argument is if it returns inconsistent answers.

For instance there are a billion or so muslims in this world. Most of them believe in islam on faith. If mslo79 told them that islam was clearly false and their reasons for believing it were wrong, and they said "Well I have faith. And to one who has faith, no explanation is necessary. To one without faith, no explanation is possible," would mslo79 accept this as a valid defence of islam? I suspect not. But if it's not a valid defence of islam, it's not a valid defence of christianity either.

Faith is simply not a reason to believe any proposition. A moment of thought shows that one can have faith in something and be wrong. An old claim some theists used was "well you have faith in your husband/wife, don't you?" But how many people who've had faith in their spouse have found that the spouse was cheating on them? It's in the millions! Clearly having faith in them does not in fact say anything about them.

Faith can be wrong. It often is wrong. Because it is not a method of determining truth, not at all.