Please, be a part of an important discussion underway here, between one Professor Squire of New Zealand, and my good self, regarding the phallic suggestiveness of horizontal top tubes. Normally, the gendering of an inanimate object is a matter of social convention. Thus skirts can be worn by men, so long as they are tartan and the men flabby and white. An architectural example: plain Doric style column capitols, by ancient agreement, are male, while Ionic style column capitols—the ones with volutes—are of female gender.
The first and second images are feminine, due to insufficient white corpulence. Yet image 3 shows white corpulence alone does not make a skirt manly. Only the dude in image 4 is combining white lard and tartan in a manner than we can agree isn't sissy.
"Mens" bicycle frames (with top tubes) transfer power more effectively than women's frames, that are wobbly. In that sense the diamond frame is sporty/manly, while a woman's frame nobbles her in the same way that her high heels nobble her. She submits to patheticness by her choice of shoes, and her choice of frame, and darlings, we love you all dearly for that.
But I want to talk in purely visual terms here. A ladies frame is itself curvacious, and feminine. A mens frame is V-shaped, like a strong masculine torso. Shall we end our inquiry there? Good heavens no, not while the internet provides us such a free space for thought. Let us talk dirty my friends. A horizontal top tube leaves less seat post exposed, thus bringing the top tube nearer to the male rider's sex organ, making the top tube a steel rod jutting forth in more ways than one! I therefore nominate the Pashley Guv'nor, the most manly bike in production, for the way it extends the suggestive forward thrusting movement of the horizontal top tube by using an extra large 28" wheel, with fat conspicuous tires, metaphorically ejeculated way down the road with those raked randonneur forks. Meanwhile, back at the testicular end, an ultra relaxed seat tube angle has brought that seat down low, and closer still to the top tube. Can't get the seat low enough, becasue you are tall? For you, mate, Pashley make Guv'nor's with double top tubes!
Gentlemen, with more people out there riding these days, it is no longer enough to have Dura-Ace gear. Garnering female attention requires a basic understanding of anthropomorphic projection.