If I got dissed in such a hyperbolic way from a boss that was paying me, I would leave.
In a situation where I've toiled in a position of importance in a project I work on in my free time, and I screwed up, I think I'd be hurt if I was dismissed lightly and without creative ire. I mean, I want to know that if I screwed up, I screwed up enough for someone to admonish me creatively, since there isn't any method of management. Your tool is primarily shame, you can't suspend someone without pay from a mailing list.