Recently, we received the response made by a reviewer to a manuscript submitted to an indexed journal. The comments were harshly offensive and humiliating, directed towards a colleague and myself, just to discredit our work (I wonder if the referee knows us personally). I think that, regardless of the quality of a paper, the authors deserve a minimum respect. In the past, I have reviewed dozens of papers, some of them excellent, others not as good but with enough merit to be published, and several that had to be rejected. In some of the latter, I even demonstrated self-plagiarism or data manipulation. But never wrote anything offensive against the authors. Just mentioned that maybe they overlooked some references, incomplete bibliographic search or, simply, the data were not valid. Not a word against the authors, personally.
My opinion is that even when reviewing a manuscript that we know is not appropriate for publishing, an ethical behavior must be followed. A basic respect to other scientists must be kept.