I was arguing with neither Teknoir nor Lewis Carrol, but only Tekla. You can't argue with Lewis Carrol, because he argues grounds for argument, and then the grounds for the grounds, and so on. I just think that you're erring equally in the other direction.
And you're doing it again. Legalities are all about bright line distinctions; that's just the nature of the beast. But that doesn't mean that those bright lines really exist in the world. Words simply have different meanings in different contexts, and fuzzy meanings in most contexts. For example, when I say "large," I could be talking about an area of 10^-28 meters -- a very large cross section, indeed, when you're talking about cross sections for nuclear interactions, as "big as a barn," as the story goes -- or I could be talking about the black hole at the center of the Milky Way. Or, you know, your mom. 😛 Jokes aside, nobody complains that certain words like "large" have meanings that depend on context and are fuzzy even in those contexts; that's taken for granted. I'm just saying that all words are like that to some extent, with some more like that than others. Sorry, the world is fuzzy and uncertain.
But then you say things like, "But, if that's so, why not ..." See, that's usually a sign warning: "slippery-slope argument ahead." It fails because the slope isn't slippery, or even all that steep. But, to tell you the truth, in the situation you described, if we just got rid of gender markers (which would require a massive cultural revolution before it could happen), I'd be pretty much thrilled. That would make my life a whole lot better. As it stands, I can deal with the bright lines defined by my state. Just don't tell me that those laws have some deep, fundamental real-world meaning. If they did, then my gender and sex would be a function of position -- talk about a radical position!