Why are you even comparing real world office life to fictional fantasy adventurer life? As civil and "well thought out" as your examples may be, it really is an utterly invalid comparison. You may as well compare game life, with the social mating etiquette of American and Japanese sea life. I'm sure there are noticeable differences in that comparison too, but they wouldn't really apply to the current issue either.
Now, let's apply your logic into the context of the actual game. If a male character enters a DF group in traditional armor, no one will "say a word." If that same character enters a DF glamoured completely in their underwear, no one will "say a word." If that same character were to enter a DF in a wedding dress, I'd say it's a safe bet no one would even care if it were a male or a female.
Yes, were this the real world, a man in a dress would get some looks. However in the game world, a "man" can walk around with a great axe, and would most likely not even get looked at. In game world fantasy terms, I really doubt anyone would want to mess with the man with the great axe, even if he were wearing a more feminine outfit. By most fictional character standards, those are the characters you really wouldn't want to mess with. Plus, I really doubt that many people, even you, would pay enough attention to even care if there's a male character in gear designed primarily for females.
Besides, I really doubt social "whatever-you-may-call-it" really plays that much of a factor into why there are these gender specific gear rules, especially in a game that allows same gender unions.