It's the
chilling effect.
Think back to McCarthyism. It only took a handful of people being subjected to 'legal' action - being labeled commies, losing their jobs, being placed on watch lists, etc. Once those first round of people were 'made an example of', the 'example' hit home with everyone else. People were afraid to be even potentially viewed as having any beliefs that were within spitting distance of communism. It didn't matter if they were actual communists or not - if they said anything that even seemed like it could be interpreted as not being 100% opposed to communism, it could result in ostracism and social sanctions, including loss of livelihood.
The same thing is happening now, using predominantly social media as a venue for enforcement. People are
afraid to even accidentally say something that can potentially be interpreted as falling into either racial or [the taboo topic]. People who are not racists, who have not actually done any racist things, have been ostracized, lost jobs, and been subjected to vicious harassment and threats... Thus, people are on edge for fear that it may happen to them. Enough so that harmless lines within a book get removed - not because there's anything wrong with those lines, but because the risk of someone deciding that this comment deserves punishment's is just too high.