Well, for starters, Charlie Sheen is not raving about tiger blood any more, because he got (and is still getting, I’m sure) help for his problems. But it wasn’t just because of his delusions that he needed help; he was a danger to himself and others.
The thing is, people generally don’t just start believing something totally bizarre out of the blue without also having other problems. If Bozuit’s friend had always believed he was a prophet, or had developed this philosophy gradually over time, and was otherwise able to function perfectly fine in life, then most people - including me - would just say, “Well, whatever.” But this sudden “revelation” indicates something more problematic, like a psychotic break, or, as you yourself suggested in the other thread, a manic episode, or some other condition that impairs the friend’s ability to function. And sure enough:
He’s been losing motivation, becoming reclusive, and failing in basic self-care, like taking medication. That’s going nowhere good. And whatever is causing that, plus delusions now, that’s the problem, not the delusions themselves. But everyone jumped on the delusions because the fact that they suddenly showed up out of nowhere was a big bright red flag, as was the fact that they’re specific to this individual, and not something shared by others, like a religion. I mean, if this friend had suddenly “found Jesus” or some other prophet, it would have certainly been worrying, given the context. But thinking he is a prophet? Yeah. There’s no way that’s not a symptom of something much, much worse.