No, there isn't.
But let me ask this: Why does there need to be? For Christians, we're called to walk by faith and not be sight. That means believing that God exists and trusting in him, even if he's not proven by human methods to be there right before us. I don't need facts about God existing in order to believe in him. It's a belief, just like believing the sun will rise tomorrow. Do you have factual knowledge that the sun won't explode while your eyes are closed at night? What about, do you have factual knowledge that a plane won't crash into your house while you're sitting there typing out a response? No, you don't. You can only believe (and hope) that those calamities, and other such happenings, don't take place. Hoping and believing doesn't make something irrational. Now, if God was proved without a doubt that he DIDN'T exist and people still believed, then there would be a problem and you could criticize all you want. But no one has disproved the existence of God, therefore, I think you should just play it safe and allow people to believe what they want, especially if they aren't making any claims. Also, as long as that belief isn't killing or harming anyone, then it really shouldn't be a problem.