Yellow-bellied is pretty silly, admittedly. I don't think "coward" is, and I think "coward" is more straight to the point than saying someone resembles a vagina. Granted, coward is not vulgar. And it's not that I object to vulgarity - I just think saying someone's being such a woman is unclear and ridiculous.

To me it's obvious that it means they think lowly of women, because (with a few words different than what you said) women are weak or pathetic or whatnot, and that's why it's an insult to be one. I guess to me it doesn't just mean "you're weak," it means "you're weak like a woman." And fair enough that femininity is weak, but I don't see it as limited to femininity. I see it as being directly related to women - maybe partly because I doubt people who use it see a distinction between "femininity" and "women."

Yeah, I have work to do as well.