Apparently, they can't. They can only claim to know.
However, I ask because:
1.) I don't view faith as a sort of Get Out of Jail Free card when it comes to difficult questions.
2.) The Bible admonishes believers to be ready to explain their faith:
"Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect ..." ~
1 Peter 3:15
Faith is what people resort to when they don't have any good reasons for what they believe.
Your objections are duly noted, but relegated to the wishy-washy limbo of the "that is fine, because that is how you see it" category that you've limned out above. Perhaps another theist will eventually bring something sturdier to the debate? I hope so.