This bit just reads like "sorry you're upset".
I would have expected something along the lines of "sorry, we should have asked the maintainers and we understand why it was wrong not to", instead of "sorry, we didn't ask the maintainers, but this is why we didn't".
Legitimately these folks have some kind of personality defect. They observed something that everyone already knew and then decided to act on it and pretend they were doing something interesting and new rather than just being twats. They should be treated exactly as should be based on their actions, regardless of their claims of being researchers. This would be a perfect cover for being on the take from a government agency. They should be investigated to ensure they aren't actual malicious actors.
It takes almost no imagination to think of hundreds of "security vulnerabilities" in the world, yet the vast majority of people realize that it's dumb to act on those observations.