It might not be exaggerated to regard a peer review report as a judgment made on the quality of your papers, and thus also on your competence. Yet some reviews can unfortunately be brutally rude. Examples are available online, l’ll only mention two here:
This paper is desperate. Please reject it completely and then block the author’s email ID so they can’t use the online system in the future
I understand that Wikipedia is not the best source for my information, however, I don’t have access to the [peer-reviewed] literature you cite, and based on the information from Wikipedia, your hypothesis breaks down.
To share I once received a review which basically said that my English is insufficient, I am probably Indonesian, and I should send my paper to national academic outlets instead. I understand this is still much better than the examples above.
According to Hugh McLaughlin in the LSE Impact Blog, we need to rethink the objective of peer review. He argues that reviews should be both “critical and constructive”. Basically, “do unto others what you would expect them to do”.
I agree, and I think as reviewers we should give thorough feedback – try to give justifications of all points made, and provide constructive feedback – clearly identify missing points and suggest some ideas on how to improve the article. Although we are at the same time authors, a role which enables us to this service, we are invited to review papers as how they are written, not how we would have written them.