But does a East Asian Confucian perspective always require it? Not necessarily.
From the Confucian viewpoint, an organization is not simply an arena for individual logical debates. Everyone has their own role and position, and when those roles collapse, the order of the community collapses.
'A superior must decide like a superior. A subordinate must remonstrate and support like a subordinate.'
What the OP's post did was not just make the boss look wrong. It declared that the boss 'could not function as a boss.' That's why the colleagues felt fear. It wasn't 'technically correct.' It was 'that person can publicly destroy the team's hierarchy.'
In Confucian terms, this is called 'remonstration without propriety.'
Good remonstration usually involves speaking privately first, respecting the other person's social face, and presenting options while preserving the form that the superior is the decision-maker. Those options should include risks and alternatives, so that it leads toward the direction you want.
In other words, you start by acknowledging that the boss's point is valid, then frame your disagreement as a risk you are worried about, but you're concerned about certain risks. If you say it that way, team members will later remember that you warned them, and the boss can't avoid responsibility either.
Of course, the boss also needs to have the right 'virtue' for that position. They need to listen to why subordinates object, and have the ability to make technical judgments. Storming out of a meeting saying 'I don't need this shit' is not boss-like behavior, so in an East Asian perspective, both sides are at fault. But many would see the subordinate who shattered the other's face as more at fault.
And of course, human relationships don't always have a right answer. I don't always follow this myself either—I fight with clients every day.