Guess what? The world is filled with imperfection.
The line of reasoning "Since I can't come up with a perfect solution, so instead I'll do nothing at all", is a terrible approach.
The courts get things wrong, credit card fraud detection gets things wrong, anti-virus gets things wrong. Tons of things aren't perfect - that's the real world.
The answer of "well I can't come up with a perfect version of those so let's do nothing" is preposterous.
Moderating "racist" comments is very far from straightforward. No one can agree what it would be.
Which of the following statements would be racist?
1. Organizations whose members are exclusively white are appropriate.
2. Organizations whose members are exclusively people of color are appropriate.
3. Blacks are a minority but commit a majority of violent crimes in the U.S.
4. Average height varies by race.
5. Average IQ varies by race.
6. Nigeria is a hellhole.
7. South Africa is a hellhole.
8. I prefer not to date blacks.
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Even Reddit bans spam but not racism.