Consider which is more effective in person - the phrase "I am angry" uttered in a calm tone of voice or profanity and insults in an angry tone of voice. One of those states anger. The other communicates anger.
I've been through military basic training, and such language is routinely used because it is quite effective at communicating error by breaking down mental resistance and barriers to correction.
In that case, the potential for emotional harm is outweighed by the net reduction in the probability for physical harm on the battlefield if such lessons aren't learned absolutely.
Make no mistake: the kind of language Linus (and so many others in our community) uses can and does cause emotional harm, primarily to people who might be called 'thin skinned'. This is discriminatory against some personality types.
In the balance between using verbally abusive language to more effectively communicate error and not doing that, I believe there's no question: verbal abuse is wrong, and should be avoided, and not defended. There are other ways to accomplish the same thing, without all of the toxic side effects.
Remember, the goal of an open source project is useful code. A friendly and emotionally supportive community is only desirable if it aids in achieving that goal.
I concur that open source projects' primary and over-arching goal is and should be to produce good code.
When the leader of a project freely (though not so frequently in this case) uses verbally abusive language, that has the strong effect of limiting the diversity of potential contributors to the project.
I'm willing to assume that a more diverse project tends to be a project that will produce better code.
In this particular case, bad code wasn't included in the project. The abusive language did nothing to stop merge of bad code.
So did verbally abusing this developer somehow cause his/her future contributions to be of higher quality? I don't know the answer to that.
Or perhaps did this verbal abuse generally raise everyone else's code quality, because they didn't want to become a victim as well? Perhaps.
One thing I am certain of, though, is that such choices artificially and severely limit the possible side of the contributor pool, and that's bad.
I'm not willing to assume that a more diverse project and larger potential contributor pool will automatically produce better code. Not all contributors are of equal value. Some contributors are of net-negative value, particularly those like Kay who persist in such. It is highly desirable to limit the potential contributor pool to as few of those individuals as possible.
Size is not the sole meaningful measure of a contributor pool. Quality is equally - and often more - important.
When dealing with matters tangential to a core purpose, sometimes the ends do justify the means. When was the last time you thanked an open source developer for stopping development on features you needed (perhaps permanently so) in order to encourage the surrounding community to be nicer to one another?
