How do you know that people don't just believe them to be all- ah, miscreants? It seems a feature of many traditions, beings either wholly alien to us or far too human – and what are people if not that?

I suppose there's no way to test that either, though. A scientific scale of arse-to-belief measurement.

Very well, Mr. Winchester. I do so solemnly promise not to sacrifice the village youths while cackling in the moonlight, and you can keep your gun down. [Not that a gun would necessarily do much to her, but he doesn't need to know that.] In exchange, and for anyone listening who is in need, I am really quite excellent at setting things on fire, and it is as good as promised for dealing with extramundane threats.

[There's a brief pause, before she hurriedly adds-]
That was unrelated to the hunters burning themselves down, I assure you.