From Holy Sh*t: A Brief History of Swearing by Melissa Moher (via Slate here) :
With the development of feminism, many swearwords have become more equal-opportunity, not less. Bitch can now be applied to men and women, as can cunt. In the 19th century shit as a noun was reserved exclusively for men — the “West Somerset Word-Book” defines it as “a term of contempt, applied to men only,” as in “He’s a regular shit.” Now, women too can work, vote, own their own property, and be called a shit.
When swearwords don’t become more equal-opportunity, they often begin to be used solely for women — Geoffrey Hughes calls this the “feminization of ambisexual terms.” Words such as scold, shrew, termagent, witch, harlot, bawd, and tramp were all at one point in their histories terms for men; furthermore, the terms were usually neutral and sometimes even adulatory. Scold, for example, comes from the Old Norse word for “poet.” When these terms were feminized, they perjorated, going from neutral or positive to insulting. Bugger bucks this trend, too, going from a word used of men and women equally to an insulting term reserved almost exclusively for men.
My anecdotal experience suggests that “b*tch” or “c*nt” are not as “equal opportunity” as the author suggests, but I’m definitely curious to read the full book.