The other day I posted about the concept of group defamation in China, noting that Chinese courts have upheld complaints in which members of a particular group sought damages or other legal remedies against those they believed had insulted their group.
The two interesting legal issues in cases like this are (1) under what circumstances can any group member sue for an insult to the entire group, and (2) what sort of commentary counts as an actionable insult (i.e., does the insult have to be an allegation of a particular fact that could be verified as true or not true (such as Donald Trump's allegation that Mexican illegal immigrants are rapists), or can it be just an offensive expression of opinion ("so-and-so is a jerk")?
In the United States, the answer to question 2 is that it must be an untrue allegation of a particular defamatory fact, not just something that is clearly the expression of an opinion that nobody would mistake for a factual allegation. The answer to question 1 is that if it's the group that has been insulted, an individual cannot sue unless the group is so small and identifiable that those who heard the defamatory statement would readily connect it to that individual. (This at least is my understanding; I'm not a libel law expert.) I note this only for comparative purposes and not to suggest that the U.S. rule is one that everyone else should follow.