Having a basic respect for another hacker's time on a project they're maintaining out of the goodness of their heart is what causes people to keep maintaining projects.
Especially since rudeness is a good way to get drama and nothing done. To paraphrase Neil Gaiman, maintainers are not your bitch. Treat them as courteously as you would like to be treated yourself.
The whine itself stinks of someone not having gone through the source to see if the product really does what they want it to do. It reeks of "hey this looks like what I want YOINK! " , implementing it in their code, and discovering afterwards that some Things are missing. Then getting pissed off at the producer of the product, rather than at themselves for their oversight/laziness.
While the tone of the report may not have been very polite, it is understandable why the reporter was disappointed.
I think it's perfectly reasonable for a user to ask that a library's deficiencies be made obvious in some way, regardless of why they exist. The readme file is a good place for this.
I don't think that Steve handled it very well at all, though. Calling the report creator an "ass" is uncalled for. Creating unnecessary drama over a perfectly reasonable request is uncalled for. Closing the bug without adding a line or two to the readme file addressing this deficiency is uncalled for. Preventing further discussion is uncalled for.