I imagine it was downvoted for its aggressive wording, coupled with the poster's later commments about 'fanboyism'.
It is perhaps to-the-point, but I don't think it is aggressive to point out that CoffeeScript frequently shows up on the front page of HN. I am guessing that the comments about fanboyism and unfair down votes came as a response to a down vote, so the initial down vote couldn't be justified on those grounds.
As to the original question of the why CoffeeScript is so popular on HN, I too would like to know.
You seem to have missed this part of my response:
Having a real choice in that space is a big deal.
Yet, they might still be moved to give a short, high level answer to the OP's question.
Those fucking bastards! :)
The closest that I can see in approach to comments is that you have to be civil and not say things in you wouldn't say in real life. The original post was not guilty on any of those counts. By no means was it an rude or uncivil comment, I see no name calling and he did support his statement in subsequent comments. If you are going to be a baby about it and can't take being called a fanboy then please accept that being called fanboy is uncivil and push to include that into the approach to comments.