The gasoline additive tetraethyl lead was totally safe. -u/zeugenie

That OxyContin had a low rate of dependency. -u/No-Discussion-3480

When Coca-Cola paid off doctors to say that fat was what caused fatness rather than sugar. This has destroyed the health of generations. It was the total converse of the truth, pushed to all American children (and many internationally), about their health! -u/andycambridge

Andrew Wakefield's fraudulent "research" claiming a link between vaccinations and autism for the purposes of selling his own "safe" vaccines. He single handedly set back not just childhood vaccinations (with a resulting unprecidented spike in measles), but fostered an anti-science sentiment that is still bearing rotten fruit in the current COVID pandemic. it's rare that you can point your finger to one person and say "YOU are personally responsible for millions of deaths", yet here we are. -u/McFeely_Smackup

When big tobacco industries made doctors endorse cigarettes. -u/Sandracotta

It might not be the worst, but when the woman who spilled hot coffee on herself from McDonald's. She ended up with 3rd-degree burns because the coffee temp wasn't regulated correctly and McDonalds paid people to make fun of her, and people still do to this day. -u/mksports

The one I think about the most is back in the 80s in the U.S. We were told constantly how the Japanese were going to rule the world because of their work ethic. Americans gave up a lot of workers' rights and time for their lives. When I finally was able to travel outside of the U.S. I heard about how Americans are workaholics. It dawned on me there was some BS propaganda going on that facilitated the current sh**ty situation in the states. -u/DrippyCheeseDog

The US FDA Food Pyramid. -u/yawmush

De Beers and their ad agency N.W. Ayer convinced America that diamonds were valuable. -u/ManEatingCow

The War on Drugs -u/PeatedPaladin

Perhaps not the most damaging, but certainly a vile example… when Pope Benedict XVI told the people of sub-Saharan Africa that condoms would actually make the HIV/AIDS crisis worse. This obviously drew extreme criticism from everyone that actually wanted to end/improve the crisis. It is a peak example of one valuing the perpetuation of their superstitious beliefs over the life of their followers. -u/P0ster_Nutbag

William Randolph Hearst printing anti-cannabis propaganda to squash the expansion of hemp that directly competed with his business. Think of all the people jailed and lives ruined. Not to mention all the applications, medical and technological, that were halted. -u/Bigstar976

Greenpeace VS GMOs Some people worked hard to modify rice to have vitamin A so has to help poor communities who did not have proper diets. Greenpeace convinced their governments GMOs are poison so tons of the stuff was burned. Children were going blind and dying and all Greenpeace cared about was the genetic purity of a plant! -u/lemons_of_doubt

That poor people are poor because they are lazy & rich people are rich because of their work ethic and intelligence… -u/Much-Diet7436

Iraq has weapons of mass destruction. 20 years later, several hundred thousand Iraqis are dead, US Servicemen and women are still suffering the effects of PTSD, and of course, untold billions of dollars lost in a failed war. -u/DarthLightside

Boys don't cry. -u/SPQC

The Protocols of the Elders of Zion. It amplified antisemitism and is still the base of conspiracy theories that there‘s a Jewish elite that controls banks, the media, etc. -u/Living_Tumbleweed_88

Nuclear power is bad -u/seanmg

That I needed a college degree to live a comfortable life. -u/easy10pins

The idea of the "welfare queen" is one of the biggest blocks to government assistance programs in the US -u/astro-chimp

Declaring news you don't like Fake News. Not actually fake news, just a cowardly device to discredit all information rather than prove what aspects of reporting you disagree with. -u/Joverol

McCarthyism completely trashed the layperson's understanding of the distinction between "socialism" and "communism" (actually it's more of a range) Now welfare and other social programs are often seen as "the slippery slope that will turn the USA into a failure like the USSR," and not "the kind of thing that just about every modern, developed democratic nation has which improves the lives of its citizens" -u/AdvocateSaint