I think Rule 0 is a very important tool for DMs. It allows DMs to shape the rules to their campaign settings, and can help create a sense of flavor. Certain cultures in a campaign setting may have strong limitations on gender roles. A DM has a right to determine what to allow and disallow in a game.
However, I would not disallow a female fighter as a character or a female player from playing a fighter character of either gender. Certain societies may have social prejudices against such characters, which is something the player will lilely see the character encountering in game. (Possibly a character might have a goal of changing societal attitudes. Or she may hide her true gender with a disguise -- something that has happened in the real world.) For myself, I would want a good
campaign-based explanation why a character of a given gender cannot pursue a given character class. in some of the games that I have played in, I have seen some effective female warriors. There are also many mythic, legendary, and historic archetypes for female warriors of all sorts.
If a DM just gives a chauvinistic response as to why a female player can't play a female warrior, then I would advise a player to seek another DM. Or to start a new game.
I seem to recall that at least one French noblewoman joined the Crusades, and their are other historical examples. Whle these examples were often exceptional, I think it is wise to remember that player characters are generally considered to be exceptional individuals.
Although women may tend to be less physically strong than men, there are exceptions. Also, the humans of a fantasy setting may or may not follow the same standards of our own world. In some campaigns, human characters might have some ancestors who were not necessarily human. So the humans of Oerth in the World of Greyhawk setting may differ slightly from the real world. (A belief in divine ancestry, or descent from some supernatural or remarkable creature, is fairly common in ancient literature as well as many ancient beliefs. I seem to recall that the founder of one of the ancient Greek city states was described as having the lower body of a dragon. Many of the characters in the Illiad claimed descent from the gods. Similar figures can be found in other cultures and in fiction -- thus giving enough in game reasons for female PCs to be equal to their male counterparts in strength and stamina.) Real life differences between the sexes may not necessarily exist in a magical world.
Ultimately, a DM decides what to allow in a game. However, I think it is a wise DM who considers the requests and interest of players. A good roleplaying campaign is ultimately a collaborative effort, where players and DMs both enjoy themselves. So, while I support the use of Rule 0 by DMs, I think it is a good idea for DMs to explain why they have made a decision on a given issue. Then the players can decide to either abide by the ruling, challenge it, or chose to leave the group.
I think we need to be a bit careful on this thread to avoid real life political or religious debates to avoid having the thread closed. (If you want to carry on such debates, I recommend going to
Nutkinland. Additonally, although I strongly suspect that the original poster was a troll, this thread has sparked some interesting discussions -- which makes this a valuable thread.