The heading about Plagiarism, over the content specifically about his plagiarism, is short and a neutral acknowledgement of fact at this point - Johann Hari was investigated and acknowledged plagiarism to his employer, who published his acknowledgement and theirs in the first two paragraphs of this news report on 15 September. For ease of reference for a new reader looking at the page, there has to be a header with "Plagiarism" on the contents list. Arguing back and forth over whether this should be lengthened by "Accusations of " is IMO a waste of space - it's a subject header, and the material under it makes quite clear exactly what he was shown to have done.