It means the publisher no longer host/publish the papers. This can be done at the request of the author or by the publisher in the case of a controversy.

In this case, it seems there is no particular issues with the content of the paper, just that the way the data was collected was not appropriate. A case can be made about the narrow set of data (focused on minority groups) and thus how representative the data is to whatever claims made in the paper. But that require a deeper read into the papers themselves and has nothing to do with the main complain, i.e. ethical concerns.