Following on from my link to The Ad Hominem Fallacy Fallacy, londonkds wonders how legitimate it is to say “This person has previously shown themselves to be ignorant/misinformed/lying/batshit on this subject on several occasions, therefore I have better things to do with my time than to rigorously investigate all their arguments this time”. I’ve replied on the original thread, but I thought I’d create a new post with my reply in:
Reminds me of Yudkowsky’s stuff on reversed stupidity and the follow up, Argument Screens Off Authority.
If someone is reliably wrong (a well informed liar), you can learn something by listening to them: you just increase the weight you give to beliefs which contradict what they say on topics where you know they tend to lie. But this might not be useful, if you already strongly believe stuff which contradicts what they say.
In practice, the people are ignorant or batshit haven’t carefully studied how to be wrong. There are more ways to be wrong than right, so they probably are wrong, but you don’t learn anything by listening to them, because their statements aren’t tangled up with the truth at all. As Yudkowsky and brokenhut say, you can decide not to listen to such people because life is too short, but that decision shouldn’t influence your opinion on the truth of their argument (though it’s hard not to be influenced in practice). So I think your quoted statement is a justifiable one as long as you don’t append “and I’ll believe their argument less as a result”.
Suber’s stuff on logical rudeness covers the case where your belief that they’re batshit is because of some theory you hold which includes explanations of how all critics of the theory are batshit (examples exist in evangelical Christianity, atheism and feminism, that I’ve seen). ISTM that such a theory can’t be used to dismiss critical arguments, though it can be used to explain why so many people apparently don’t believe the theory.
(You can comment on the original post: I’ve disabled comments on this one to keep all the discussion in one place).