It is your own choice if you wish to continue the maintenance or not (and, even if you wish to maintain the project, you can decide to not accept email messages

It is your own choice if you wish to continue the maintenance or not (and, even if you wish to maintain the project, you can decide to not accept email messages). If it is FOSS, then other people can maintain their own version if they want to do, anyways (this is why FOSS is important; it is due to things like this). However, whoever wrote the email message did not decomission the project; it is whoever maintain the project that did so, due to receiving such email message. I think that might be unnecessary to decomission the project just due to one message like that, but it is their choice to maintain or not maintain it, or to decomission it. (Anyways, if you receive too many messages like that then you might be too stressed to work on the project properly.) Although, still they should not have written such a email message, because it is no good. It does contain an actual comment about the program (although I am not familiar with the program to know whether or not the complaint is legitimate), but that is a very bad way of writing it. (Other comments also mention that stuff like this may be used to attack the project to make a version with malware if the original maintainer won't then someone else will and will add malware. It is a legitimate concern, which should be considered seriously, but one that can be handled whether or not this maintainer decides to maintain this project or not.)