Unfalsifiabile theory is just metaphor
If someone is using an unfalsifiable theory to tell you something, they are really using a metaphor and you should treat it like one. Listen to them. Stop inventing logical fallacyesque copout why someone should be treated like they’re in a formal debate instead of trying to communicate something.
If they are trying to ‘prove’ their metaphor there are usually one of two things that’s happening: (1) They have smuggled in aspects that are falsifiable, but they don’t know how to articulate them. (2) They are secretly (perhaps to themselves) trying to get social consensus as proof.
The second problem is often viewed as malice, but it is largely an understandable conflation. Most people (including most scientists) don’t have a strong enough working knowledge of falsifiability that they conflate social certainty with falsifiable claims that have stood up to attempts to reject the claim. After all they have been explained the truth of lots of falsifiable theories without the accompanying evidence: how many people do you know who can explain why we know our solar system is heliocentric?