Below is a script where I attempt to explain in a non-dry way, by a somewhat humorous example.
Who has the burden of proof?
After all, if he really teleported to the crystal cities of mercury he's the one who would have access to the evidence.
The others he's trying to convince weren't there so how could they have brought their cameras to prove or disprove it?
As Fred was the one who went, he knows how, and he knows how to do it again. The others don't.
On the other hand...
He didn't really teleport to mercury with his mind.
It's a good thing it's up to Fred to present evidence before anyone else should take him seriously.
Otherwise, the others would have wasted the only life we know they have, trying to debunk his claim.
If Fred's claim is frivolous, foolish, fraudulent or fanciful, he's only managed to waste his own life.
So, Fred, and his thousands of erroneous brethren, have the burden.
If Fred claimed something mundane that has consequences, like a child trapped under a nearby car, you should probably look into it.
If Fred claims something dire that sounds crazy, such as saying that intergalactic space manatees are coming to eat you and digest you forever, you can ignore him until he can back up his claims better, because it probably is crazy.
We have a life to live without wasting it chasing fantasies.
The last section at the end is my trying to address this rebuttal about a "burden of investigation" - whether the potential consequences of not investigating warrant overriding the burden of proof.
On another note, I mentioned before that I was trying to focus on the visual animation before the script. That approach failed. I found myself directionless and unable to make any progress. I create a script, and all of a sudden, direction!
I think the compromise is that I also write a visual script side-by-side with the oral script. Before, I'd get to the point of having processed recorded audio of the oral script, in the animation software, before I'd give a single thought to what would actually be animated.
At that point, it's too late to make changes to the audio.
Here, I can change the oral script to be more conducive to the visual script before doing any recording.
This may work better.