There is no objective morality. Coordinated shunning is Bytemaster's subjective morality.
Given a difference of opinion on the existence or not of objective morality on another thread (IMO, an example of things that are subjectively objective - i.e. everyone has an unprovable opinion), I was giving an opportunity for an objective and irrefutable case to be made here.
However its clear that most respondents here believe shunning has a quite subjective morality. Going further, there appears to be a majority suggestion in this thread of what I might label "functional morality" (though there may be a better defined existing label), which I will define as "something is deemed moral if there is functionally no alternative in order to preserve that which must be preserved at all cost". So in this case, for society to function, some form of action is deemed to be required to preserve order in society (without which the society does not exist), and shunning is considered to be the least-cost least-violent form currently available. A similar moral argument would apply to self-defence of one's life, or those of loved ones. I lean toward this functional view myself, but it may not be the best approach to weigh morality. Clearly, what fits the category of functional morality would also change for society over time.
However I would feel more comfortable if "coordinated shunning" were replaced with "distributed disclosure", for lack of a more catchy phrase. This only obligates transparency, but not on others to interact with the person or not. For example, based on the evidence available, if somebody was known to have broken the terms of a partnership contract, I would not refrain from selling goods to them, but if they had a history of non-payment for goods, then clearly this would be a risk in this type of dealing with them. And if I chose to deal with that person, I would not expect to be judged (or worse, potentially shunned) by others. Choosing to deal with somebody would be voluntary and case-specific, and not coordinated by any sort of authoritative process. I do not feel it is moral to condone the shunning of someone in all dealings irrespective of what I thought of that evidence, its seriousness, and its relevance. This makes it more challenging for the transgressor to partake of that particular activity, without becoming an outcast in society, although it is not as forceful on them to make amends either.
There are other big-picture questions as to the effectiveness of such measures in a global community and whether violence between groups of differing values can ever be avoided anyway. But I agree with the intent of where this idea came from - it is definitely necessary to find alternatives to imprisonment and threatened violence.