There are reputable journalists of statute besides Seymour Hersh, and I think you'll have a hard time finding one that believes Hersh's claims about UBL. That people on message boards find him convincing doesn't tell us much; there were people on HN who believed PizzaGate.
Also had a harm time finding a scientist at NASA willling to support the foam strike hypothesis. Semmelweis showed hard evidence of the efficacy of hygiene in saving lives, but was an absolute pariah, literally driven into a mental hospital by his critics. There was a Nobel given to a physician for the lobotomy procedure.
Point is if you just trust the methodology of using groupthink to determine righteousness you will get some things wrong. And it gets really bad once we venture away from scientific fields. You can see in history people's psyches sometimes coalescing around acceptableness of some pretty horrendous ideas like inquisitions, holocausts, abu ghraibs, etc.