Facing Challenges
Systems are challenged in their self-acceptance, day in and day out, from without and from within.
Here's what to look out for in the wild, and what that one internal conflict might just boil down to.
Normativity
Outside of basic non-acceptance or misunderstandings of the nature of plurality, the most widespread root of sysphobia is singlet-normativity - the idea that singlethood is a privileged default expected of everyone. Because wider society is not exposed to plurality, deviations from expectations associated with a singlet identity model can lead to rejection, distress, and danger.
Though a lens where singlethood is the only "normal", plurality is unacceptably complex and must be a fabricated delusion, the privacy of a system is irrelevant compared to keeping others aware of the abnormality, and the needs and desires of a system can be dismissed in pursuit of restoring that normalcy through medical intervention.
This creates a pressure to be "normal enough" that affects systems far beyond the point of self-acceptance. Whenever a system un-represses (or "gains") a new headmate, they're challenged with the question - how many headmates can a system have without becoming unacceptable? Faced with normative pressure, "a System of 2/3/4" feels more believable and acceptable than "a System of 40" - even when both systems comfortably understand themselves. It's not just numbers either - whenever a plural experience doesn't line up with the simplest, most widely propagated analogies, it instills this fear.
Through this rejection of plural diversity, restrictive definitions of plurality emerge. Singlets with these limited understandings can easily leave one system feeling objectified (treated as "fun costumes"), and another unable to express their systemhood (treated as purely individuals). And of course, without a widely propagated diverse definition, questioning systems are left wondering if they can call themselves plural at all.
Imposter syndrome, and the feeling that you might be being plural wrong, is pervasive. However, this struggle is not purely internal - many systems turn that fear of abnormality towards others, choosing their own imposters to exclude instead.
Sysmedicalism
Sysmedicalists are those that ostracize systems for lacking a medical diagnosis, or otherwise adhering poorly to medical models of plurality. Through these criteria, systems are excluded from communities and support, and experience targeted sysphobia (e.g. accusations of "faking" systemhood) from what should be their peers.
This targets a substantial population - DID and OSDD diagnoses exclude many systems by focusing primarily on individual traumatic history and self-reported criteria like personal distress. Additionally, this places pressure on systems who fit these criteria to get a diagnosis, whereupon a mix of limited recommendations and poor practice means they invite medical discrimination (including a pressure to get "fixed") or even genuine danger to themselves in the form of rejected voluntary medical procedures or psych ward discharges.
Sysmedicalist beliefs and language are widely propagated online, especially exclusion focusing on whether a system exists "through trauma" ("traumagenic", which is deemed acceptable), or through some other mechanism ("endogenic", which is deemed unacceptable). This is naturally not falsifiable - there's no way to validate that you possess an objective and correct understanding of the reason a system exists as it does, even in yourself. However, by propagating the two key terms as an objective categorization of all systems, online discourse is twisted towards whether "endogenic" systems are acceptable - rather than whether these classifications are appropriate to use, or even possible to define.
Syscourse
On a finer level, all kinds of systems are ostracized for having specific experiences - with a majority of systems and purported allies having a "weird" or "problematic" line above which a system being visible in public becomes unacceptable. Most of this discourse relies on applying a generic, singlet-like interpretation to plural internal experiences, as well as language used to describe them.
Taken this way, all of our previous nuanced examples can easily be made objectionable. The Minotaur is cultural appropriation, intrasystem relationships are cheating, familial terms are disrespectful to "real family", Fictives are copyright infringement and stealing, and the cultural and moral expectations of family members, children, and animals in the outside world can be placed strictly on headmates that resemble them - inviting exclusion based on singlet definitions of irresponsible caretaking, immaturity, and inhumanness - along with the occasional accusation of incest, rape, and bestiality.
Seeing past this moral panic requires a certain nuance towards experiences, identities, and activities that outwardly resemble outside-world bad behaviour but have little capacity to do actual harm. This is also the subject of similar-sounding online debates around depictions of conventionally-unhealthy relationships in fan works (proshipping discourse) and those around reinterpretations of (usually, young) characters for pornographic fan art (aging-up discourse). Through similarities to their own identity, a system can be personally affected by these debates - or even made into a target themselves if they resemble a relevant fictional character.
Engaging with the stranger, more complex details of a system requires a level of trust - and many systems are forced to carefully navigate this trust in order to avoid unnecessary conflict.