This is a list of things that people believe, based on "Studies" that have been debunked or discredited.
There was this huge scam for many years that bees were dying, and it was going to be the end us of all, because bees were so important to the ecosystem. Colony Collapse Disorder was sensationalized as the greatest threat to humanity since Nuclear weapons. A decade later, nothing had happened and most had forgotten the media's sensationalism. But the informed remembered, and learned from the mistake.
Stanford Prison Experiment
There was a study done by Professor Philip Zimbardo in 1971, which divided people into two groups: guards and prisoners, and within days the prison guards had become brutal monsters and the prisoners hapless victims, showing that authority corrupts, prisons are bad, and victims are noble. Or at least that was what confirmation bias it showed to those 1971 hippies who wanted to see the man as evil and the individuals as noble.
The truth was it was a flawed study that has never been reproduced. Zimbardo was not impartial and had egged both sides on. One prisoner admitted he faked his breakdown, and led a "rebellion" as part of the act. They were tainted by knowing it was a game/experiment and they couldn't be hurt. The guards had been told by Zimbardo to be nasty, and his graduate student playing the warden was goading all the guards to be more brutal. The guards claimed that they thought this was an improv exercise, so played along the role they were told to play: not neutral guard but the bad guy in "Cool hand luke". Zimbardo claimed it was all genuine, even though people on both sides of the experiment disagreed.
The conclusions shouldn't have been that humans are inherently evil when in power, but that humans will often do what they're told and play along. Especially if they're college students at Stanford, in the early 1970's.