You can certainly ostracize people who don’t deserve to be ostracized, but it doesn’t follow from that that all social ostracization is inherently bad. Freedom of association and freedom of speech can be used for bad ends as well as good, like most freedoms.

Who gets to decide what ostracization is good and what ostracization is bad?

I don't think anyone decides that as such. Organizations and individuals decide who they do or don't want to associate with. If it turns out that very few people want to associate with you, then you've been ostracized. Your question is like asking "Who decides which people should be friends?", or "Who decides who should be popular?"

> Organizations and individuals decide who they do or don't want to associate with

No they don't, there are laws against that, for example you can't decide to ostracize black people from your company, you will get sued for that.

Hmm? There are laws against some forms of discrimination, but organizations have freedom of association just as individuals do. For example, political affiliation is not a protected class, so (in some states and some contexts) it is perfectly legal for a private company to decline to hire someone on the basis of their political views.

Thinking in terms of the US constitution and the laws built on top if it, ostracization by the government is forbidden and ostracization by private citizens and entities is not.

> ostracization by the government is forbidden and ostracization by private citizens and entities is not.

So its fine to fire all black people to ostracize them? No, of course not, so no you are wrong here, there are more limitations than that, people have rights protecting them from a lot of ostracism.

Yes, there are some narrow carve-outs, to encourage ostracization on the basis of behavior rather than the basis of identity.

This works because people can choose to not be jerks, but they can't choose to not be black.

And who would hold everyone in the group to that standard? How do you stop a lynch mob?

The police, that is how we stopped lynch mobs in the past.

Ostracization is an absolutely critical tool in the marketplace of ideas.

I'm sympathetic to the argument that the dynamics of the Internet have made some tools more or less suitable for purpose as what they used to be, but the idea that we can just assert "no ostracization" is flatly insane and totally antithetical to the marketplace of ideas.

Like I said "Not saying this as a value judgement, just that this practice is ancient."

Heck, downvotes here in HN are basically the same thing. If a statement doesn't comply with both the explicit rules and implicit assumptions and culture here, it will be downvoted to oblivion. And it is one of the major mechanisms that HN uses to ensure this site remains useful and relevant even with the large number of participants.

And that leads to a monoculture and echo chambers.

Just because something applies some negative pressure on diversity of thought doesn't mean it necessarily "leads to a monoculture and echo chambers."

If you're in a car that's going way too fast, do you tell the driver not to touch the brakes because it "leads to us never reaching our destination?"

Anyway, we're currently seeing the reign of the "cancel culture is the big problem" crybabies. Turns out they just thought the state should have the power to decide who's allowed to have an opinion.