> Don't update positively on your extremist beliefs whenever you hear a bad argument against them

Two problems:

1. There are beliefs people hold approximately as strongly as they hold "the Sun will rise tomorrow", so "updating" is kinda irrelevant.

2. How many people actually think any of their beliefs are "extremist"? And if they don't, they won't consider the warning to apply.

And after digging in further:

3. Many people reasonably believe that their discussion circles already filter out a lot of "average people" and thus expect a higher standard of discourse from their ideological opponents. When that still doesn't happen, it naturally seems like stronger evidence.

4. (Insert generic annoyance at veganism discourse here.)