Profanity is hardly the only thing. HN, or a subset of it's users, basically expect everyone to act like humourless, passionless robots.

According to Paul Fussell's Class: A Guide Through the American Status System, aversion to profanity is a middle class thing. The upper class[1] do not use euphemisms for profanity or obscenity. Fussell wrote that Jilly Cooper reported "I once overheard my son regaling his friends: 'Mummy says pardon is a much worse word than fuck.'"

I doubt that many members of the upper class (see Fussell's book for a definition of upper class, it is roughly the tastes of "old money" but not dependent upon actual wealth) read Hacker News. It is likely that those who do not object to obscenities such as the word "fuck" are more socially liberal freethinkers who dislike formality. Those who do object are likely to be members of the middle class who believe (foolishly) that in censoring profanities and vulgarities, they are emulating the upper class.

[1] http://www.amazon.com/Class-Through-American-Status-System/d...