While I somewhat agree with his position, there are a few reasons why people "self-censor". Only one of them is fear. Another is that civil society depends on pulling together with a lot of conversations on non-controversial topics, and only occasionally talking about emotional and controversial topics that pull people apart. Since others bring up controversial topics too often (often in search of clicks/attention), not bringing up controversial topics is an attempt not to make a bad situation (polarization) worse.
It's kind of how shouting "everybody shut up" at the top of your lungs, does not usually help to quiet things.