Regarding your experience with your client, I will say that to this day, many years after falling into that first rabbit hole, I'm still shocked at some of the things They do. Not shocked enough to disbelieve the evidence before me and it's implications, but I'm saying it might have been something I previously thought They would not do.

After long contemplation on the matter, I came to the realization that the limiting factor was actually** imagination**. If you cannot imagine something might be true, you'll overlook or misinterpret or reject evidence for it, or fail to notice it in the first place. You will fail to give ideas consideration, since imagination is used as a heuristic to immediately reject ideas that are "not possible".

I would suggest that your client never associated the shingles vaxx with the negative health effects because he thinks it's impossible that every vaxx might be a form of bioweapon. And he thinks that because he literally cannot imagine that it is true.

And all of this takes place at a subconscious level, so he couldn't even walk you through the thought process as I just did, since it is not a process of conscious thought at all.