The TOS specifically mentions bigotry based on gender yet I've seen far too many examples of people claiming there's no ban on sexism. Based on which word is used, the term may be 1)nearly always sexist, 2) sometimes sexist, or 3) sexist rarely or never.
This isn't a word war. Word usage is only a part of sexist behavior. Using frames that play off stereotypes, particularly crude ones, are IMHO a bigger problem on DU.
As for imposing standards on the broader community that are better accepted within certain groups, that's not the issue. It's clarifying what constitutes the existing standards for the broader community which is why it's a TOS issue. The TOS on bigotry has examples to amplify some of the prohibitions but there's no example for gender bigotry. On top of that, I've been quite surprised to read many DUers claiming that bigotry based on gender is somehow unrelated to sexism. Adding that word as part of an example would help clear up that misconception.
As for insults always being insults, that only holds true when all of the readers are using similar references to assess the insult. For example when a New England grandmother says "Bless his heart" it is absolutely, positively not an insult. When a Southerner uses the phrase, it may be indeed be an insult.