To a normal person, face-to-face, this would refer to the idea that you began a discussion with opposite viewpoints but never had any intention of engaging with the other speakers constructively or with any positive intent whatsoever, i.e. you meant to emotionally wound someone or get them heated so that they embarrassed themselves in public.
The real definition of "arguing in bad faith" would be pretty close "being devils advocate without letting people know". The crux of it is someone is accusing you of arguing in bad faith, they are telling you that you secretly believe something else other than what you're arguing.
Why does the speaker's actual belief matter to the discussion, if the speaker isn't being dishonest? For example, if I hear someone make a fallacious argument against creationism, even though I don't believe in creationism, I would disagree with their premise.
Cancer doesn't excise itself though. That's more like a chestburster.
Closed Mind has some specific connotations in this context that I think might confuse things, because having a closed mind plays a role but the deception about being closed minded is key to the equation, the wikipedia quote on "bad faith" generally sums it up fairly well:
Great, on top of being a left wing shithole, that site has scams and malware disguised as ads. Can it get even worse?
Well we just need the owner making pleas for money on a monthly basis for bandwidth and server costs (but that actually get spent on box wine and ambien), a confirmed convicted pedophile on the mod team, and a subforum dedicated to doxing current users, and its transformation into peak somethingawful would be complete I suppose...
