Anyone can communicate or do other stuff that will affect anyone, and they may make decisions based on that. Therefore, it is both of their fault. Whoever wrote

Anyone can communicate or do other stuff that will affect anyone, and they may make decisions based on that. Therefore, it is both of their fault. Whoever wrote the email message should not have written like that; but, it is the receiver to decide what (if anything) to do about it. The maintainer can choose to decomission the project; whether or not that is the best thing to do is a different question (although, considering what the first paragraph of the README.md file says, there are some reasons that they might not want to work on this project, especially if all it results is email messages like that one).