And no number of people saying this seems to make this meme go away.
Well knowledge wasn't spread as easily, and could be lost. People knew, then they didn't and so on. It doesn't detract from my point that flat earth is an example of an idea that died off when more people learn about it and scrutinize it.
> In the end, slavery wasn't abolished by debates: it was abolished by literally sending troops to shoot slave owners.
Abolishment of slavery took many angles since it was a massive change of society. Sure, you can pick one country where it required a war. But that doesn't mean the battle of ideas aspect is any less important. Even to rally troops you need to convince them their ideas are worth fighting for.
> (communism) still accepted widely enough to turn Russia into Soviet Union
Sure, and then we saw the results, and the bad idea died off (mostly)
And the USSR, #4 was Communist until it collapsed economically, not intellectually?
I'd say it died off for generations because of active deplatforming of anyone involved rather than an open debate on the merits. For instance it was literally illegal to be a communist in the US due to the Communist Control Act of 1954.
That people thought the Earth was flat before Galileo is a meme. Even Ancient Greeks knew it was round.
> pro-slavery views
In 1776, America is born with its Freedom(TM). In 1829, Mexico abolishes slavery. In 1835, Texas revolts, resulting in Republic of Texas (1836), which then merges with the US (1846), which triggers the Mexican-American War (1846-1848), which leads to, among other things, recognition that Texas is a part of a slave-holding nation. Slavery won't be abolished until the Civil War (1861-1865).
In the end, slavery wasn't abolished by debates: it was abolished by literally sending troops to shoot slave owners.
> communism
Karl Marx wrote Das Kapital in London while writing articles for New-York Daily Tribune. Whatever its merits are, his ideas were widely known throughout Europe, and still accepted widely enough to turn Russia into Soviet Union.