There's a huge difference between being mistaken once or even frequently and promoting (by definition non-falsifiable and thus unscientific) conspiracy theories. Many important scientific theories or observations turned out wrong later on and their authors remain respected. The chance to be disproven is a hallmark of science.

Can you give such examples? I have never heard this, all scientists make mistakes.

Isaac Newton believed in alchemy but we haven't thrown out Newtonian physics because of it.

@user111388 here are some examples: en.m.wikipedia.org/wiki/Superseded_theories_in_science

John Nash is an obvious counterexample. He did some great mathematics in the 50s, then got so delusional and paranoid that he had to spend the 60s in and out of mental hospitals. But by the 90s he somehow managed to recover and slowly returned to academia.

Fred Hoyle comes to mind as an interesting example. He is really moving along the extremes.

@henningReinstateMonica: Could you clarify your examples? Which accomplished scientists lost their credential after the theories were disproven?

The point of a scientific theory is that it can be proven wrong. If it can't be proven wrong, then it is not scientific. So anyone that supports a scientific theory can be proven wrong. That is part of the job, and when it happens that does not discredit you. So your observation that science is unforgiving is false in that respect. However, it can be harsh with respect to other errors.

Could you clarify what you’re meaning by “conspiracy theories”? If it’s the GM streetcar conspiracy that’s a different kettle of fish than if it’s that Queen Elizabeth is a reptilian.

@mlk That has nothing to do with pseudoscience, that relates to a mental health condition.

Also Newton kept his research on alchemy to himself as far as I know so not really valid, I don't think he was trying to publish on it or push it upon other people.

@Tom No, but a lot with conspiracy theories, which were the other thing mentioned in the question.

Jean-Claude Pressac may be another example.

If Newton kept his alchemical research private because he had no results to show for it, then he was being an exemplary scientist.

I'm flagging Nature's Harmonious Four-Day Time Cube because it is running on TempleOS and there are no fringes on the flag that disclaims the admiralty jurisdiction on our educated stupid schools.

Discarding someone’s argument because they have been wrong previously is an ad hominem fallacy (en.m.wikipedia.org/wiki/Ad_hominem). In academia, this fallacy is often willingly committed (in many cases rightfully so) due to time constraints and efficiency considerations.

Are we excluding cases of subsequent vindication? Quasi Crystals and Quasi-periodic tiling? Within the lifetime?

Why would we not judge a source by their credibility? Of course we can and do . Even if everything shown in a paper were justified a dishonest source might be simply omitting material damaging to their claim (/agenda). That also makes clear that deliberate falsehood is night-and-day worse than an honest mistake.

I would like to see a few examples as well... @henning--reinstateMonica, it doesn't seem the author is talking about superseded theories that we later found out to be wrong. "conspiracy theories or something else obviously false" is mentioned.

@EvilSnack not really. If he had results which shows alchemy didn’t work then (by modern standards) he should have published. Hiding results you don’t like isn’t good science.

Or maybe it was sketchy. Perhaps due to some error his efforts did not achieve consistent results, and he did not think it worthwhile to publicize this.

"...lot of psychologists claiming that conspiracy theories are hopeless..." Psychology itself is full of pseudoscientists, no rigour and anecdotal evidence.

As a Dutch proverb says, trust comes by foot and leaves by horse. This applies to a lot of things in life, but it does not imply that false statements or beliefs forever deprive you from redeeming yourself, especially not in the rather rational field of science.

I don't think people lose credentials for making disproven statements (unless the credential itself was gained on the basis of fraud). They probably lose credence.

Scientists (and people in general) don't lose credibility when they make incorrect conclusions. They lose credibility by being intellectually dishonest. People who dwell in pseudoscience are invariably intellectually dishonest and should never be trusted for anything, while credible scientists who later proved wrong can still be credible source for pretty much anything except the the single disproven conclusion.

The difference is that "making a staement" is not the issue. The issue is "making an absolute statement that lacks facts and references to back it up" is an issue. When you do the former, yes you get burned. When you do the latter - which will often include words like 'in the sample that I observed' or 'it may be possible', it makes these statements ok.

-1 Half this question is about making "statements that turn out to be false" and half is about pseudoscience/conspiracy theories. A lot of it doesn't make sense. Please focus on one or the other.