It's a major over reaction by the other person to file an MIR for one comment.
However, as a member of two projects where I receive emails for comments posted on project managed profiles, there are emails coming through on a regular basis where people are offering potentially useful information about the person featured in the profile, which can be added to the bio. Others are visitors to the site with a query about the profile or they are wanting information about their ancestors. In the midst of this is a never ending stream of emails from people who think we all want to know that this person is their 23rd cousin 6 times removed, or whatever their relationship is. Sorry, but this is of no interest to anyone else except the person who posted the comment. If it is a popular profile with some controversy, there are already lots of comments from people providing info relevant to the bio. Comments about distant relationships are contributing to clutter. They're also annoying people who already receive a lot of emails for project managed profiles. So whilst to you it is only one comment, that may not be the case for the person who blew up about it. Comments about distant relationships and connections are probably best placed on your own profile.