While the authors' reaction is understandable as the software is free, it's also important to take emails like this to heart. Emails like this come from a place of frustration, and there's usually some underlying issue that can be found and improved on. Sometimes users have been frustrated for a long time, and the small issue at hand is irrelevant. It's the whole experience of the software being too cumbersome that leads to a user throwing in the towel sending an email like this.