Well, no, because you’re missing my point.
The goal in pointing out bad faith is not necessarily to make the thread go back on track. As you say, the thread may be unsalvageable. If the thread was bad faith from the OP, it probably is. But that doesn’t mean that the acknowledgement does nothing. Threads don’t exist in isolation.
The point in pointing out bad faith is is to discourage such discussions, not necessarily to salvage the original While it’s great if the thread goes back on track (if it ever had a track to begin with), it need not do so, and likely won’t unless the person arguing disingenuously actually has a real argument.
And I do have experience with success with the way I deal with such arguments. Sure, sometimes I just get ignored. But I’ve also seen the people I allege arguing poorly stop arguing in a disingenuous manner. And I’ve seen them stop arguing altogether. I’ve seen people who were arguing in good faith with them stop wasting their time, realizing it’s pointless. Sure, the threads often continue with a few posters bickering back and forth, but the thread ends.
I have specifically noticed certain disingenuous arguments decrease. No more “people have different opinions” arguments without actually defending the opposite opinion. I see fewer attempts to let sarcasm be a substitute for an argument. And I see fewer instances of people just telling me to shut up or imply that I’m stupid (when they can’t say it directly) instead of actually arguing that I’m wrong.
I do know that nothing is accomplished by simply ignoring that an argument is disingenuous and arguing it anyways. All that does is allow them to control the narrative, and encourage more such arguments. And I know the mods are hesitant to call out any but the most egregious examples.
Hence my advice to use statements that don’t directly accuse them of bad faith arguing, but point out how their arguments are bad. When I say “sarcasm isn’t a substitute for an argument,” I am technically only saying “your argument is bad. Why not try arguing instead of mocking.” Or, more relevant to this situation, when I say “You seem to be asking a lot of questions. What is your view on this?” Or “You claimed to be neutral when you started, but now it seems you clearly have a side in this. Why not state it directly so we can have a proper debate?”
I do genuinely think these things help. If they don’t fix the thread, they at least show that we notice when people are trying to avoid direct argument, and thus encourage them to not continue doing so.