What was one of the things people believed in the late 1960s and early 1970s that wasn't true?

The one in college that was circulating a lot is that Cigarettes by then people knew gave people lung cancer and other forms of cancer. However, people believed for some reason that marijuana smoking didn't cause lung cancer and other types of cancer. So, this is one of many of the false claims that circulated in High Schools and colleges at that time. So, I wonder how many people have died from lung cancer not caused by cigarettes or cigars or pipe tobacco but from smoking Marijuana instead, especially because it is legal for adults so many states in the U.S. now.

There was always this false belief that because marijuana was organic like many other plants or could be grown this way that somehow it was superior to other things people might use which were highly processed in one way or another. So, these were some of the false beliefs circulating in High schools and Colleges in the late 1960s and early 1970s then.

But now, with Social Media people can state literally anything and some people who don't have critical thinking skills are going to believe them which might kill them in some way, shape or form now too.