Sometimes that fringe scientist turns out to be right. Ideas should be judged on their own merit, not based on the resistance of those who've built their careers on the currently accepted ideas.
Deliberately sampling an “unbiased” subset of an actually biased underlying population is not just allowing the heuristic to stray from reality, it’s deliberately destroying that heuristic and deliberately misleading people. In imaginary “everyone can/should judge on own merits”-land, that’s perfectly fine. In reality, where almost no one can actually judge almost anything of substance on its merits, you are actively sabotaging truth-seeking.
The way that fringe scientist gets to declare s/he is right is by convincing their peers of it, not by convincing the public in a format that violates the heuristics the public has to rely on. Of course everyone should always be open to this possibility, most of all their peers (and to your point they often aren’t!)
What's of even more concern to me is the prevalence of this in the HN crowd - ostensibly a bunch of very intelligent people with expert knowledge in their respective fields and who thus understand what goes into actually understanding something...
Do germs grow in a heated, sealed flask? No. Clear evidence for germ theory, disproving the accepted view at the time, spontaneous generation.
Do nuclear fission and modern electronics work? Clear evidence for quantum physics, even though Einstein argued against it till the end.
Is GPS accurate before or after adjusting for time passing faster in orbit? (After.) Clear evidence for general relativity, despite how wild it seems.
On the other hand, when a group of people collectively tell you their ideas are right, and that other ideas are "fringe", without clear evidence, that's an ideology or a religion.