http://blog.ycombinator.com/new-hacker-news-guideline
"Critical thinking is good; shallow cynicism, on the other hand, adds nothing of value to the community. It is unpleasant to read and detracts from actual work. If you have something important but negative to say, that's fine, but say it in a respectful way."
https://news.ycombinator.com/newsguidelines.html
"Avoid gratuitous negativity." "Resist commenting about being downvoted. It never does any good, and it makes boring reading."
I've always felt that this was wishful thinking on the part of the mods. Discussions about downvotes (or completely legitimate questions as to why something was downvoted) are no more boring than hundreds of other topics discussed here every day.
I think the word is justified in this context however because the rationale behind immunotherapy is very sound, and it seems able to cure a non-negligible proportion of patients with otherwise incurable disease.