It's odd, or perhaps it's not odd, that we use the same word for 'extremely angry' and 'deranged'. Perhaps angry mad is more likely to be transitive: mad at ...
Psychotic mad is conventionally less intelligible, but in both cases the principle of charity is involved - we have either withdrawn it, or are threatening to. Someone who is mad cannot be, or possibly cannot be, 'reasoned' with - they are, or may be, outside our 'language community'.
Our desire to explain this to them is, of course, evidence of bad faith. Or, at least, of lack of imagination. If we can't talk to someone, we can't tell them this either. By itself, this should make us cautious of our judgments in this area.
The experience of leaving a 'language community', or of experimenting with its boundaries, may be disturbing, depending on how the community is policed. A shared idiolect may be comforting while at home, but unless it is 'open' it will require wholesale rejection of 'others'. Some online information silos are like this.
A closed language community will always appear liturgical to an outsider, because the 'why?' questions that they need explicit answers to cannot be asked within the community - they would make it 'open', rather than 'closed', and make its members feel unsafe. The cult convert is always odd because they have had to explore the boundaries of the liturgy in a somewhat self-aware way (even if they don't share this exploration with other cult members once they are inside). In order to join the cult, they have had to translate the liturgy - render it (minimally) intelligible, as well as simply tractable.
The experience of being near a boundary, being forced to explicitly address the issues it raises, can simply feel like incongruence. We don't know whether the people on the other side are being perverse, or ignorant, or whether they might even know something we don't. And they might feel the same (we have no shared tools for exploring this symmetry at this point).
I suppose I'm feeling my way towards a conception of 'mental illness' that has to do with language acquisition - feelings of being 'unable to make sense'. And contemplating the consequences of finding ourselves without a language we can use to discuss this ...
