It doesn't need to be argued it's a perfectly valid reason (and has been reaffirmed by different DPAs), the GDPR does not define what a valid or a non valid legitimate interest is, it just has to be well defined and transparent.

I suggest you read the "legitimate Interests" part of the document you provided.

>It will be argued the marginal value of each additional exposure of the reader's private data does not outweigh the individual's right to privacy.

There is nothing in the GDPR that puts on legitimate interest over another including your so called right to privacy.