As I understand it, there are two “types” of excommunication. There is the de facto type - as in a person who excommunicates himself, and the official type where the Church imposes excommunication as a punishment - similar to a judgement against a convicted criminal.
In the latter case, how should we respond towards those who have been excommunicated? Should we shun these people? Since the intent of excommunication is to get people to repent and return to the Church ( I think), would our continued support be somehow circumventing the efforts of the Church.