Well, I mean, let's name the fear here. The fear is that without subtractive masculinity (great phrase!), men are simply womb-disabled women...The phrase is not mine, by the way, though I agree it is a good one. It's also the way masculinity truly is defined, as "What Women Do Not Do", and that is why any advances women make are seen as threats to subtractive masculinity. You chip-chip away at the tight boundaries of traditional femininity, and you think you are increasing freedom and fairness, right? But from the point of view of subtractive masculinity you are leaving men less and less space to be men.
Because that space is defined by women not being there or being incapable of being there. Fascinating, is it not? Subtractive masculinity means that every attempt to increase women's rights decreases men's rights in the emotional sense. Everything becomes a zero-sum game! If women win, men lose! And naturally the other way round.
I have finally understood (in the emotional sense) how people in this still-mostly-patriarchal world can honestly and seriously worry about the "end of men" and similar concerns. I thought people writing those stories just wanted to get clicks by being outrageous. But they view masculinity as subtractive. So of course the fact that women's spheres of life have widened must mean that men are worse off! Of course. It does not matter at all that women are still doing worse than men are. Any improvements are encroachments on that holy ground of subtractive masculinity.
This concept also explains much better why the traditionally male blue-collar occupations are so resistant towards any entry by women. The very presence of those women dilutes the masculinity signal that being a roofer or a carpenter or a plumber gives a man. Men build houses, not women. Women clean them. If women build houses, what are men? House cleaners?
There is more to subtractive masculinity than is initially apparent, and that last example demonstrates it. There's no real pressure to expand the definition of masculinity to traditionally female areas of work, such as house cleaning or child care. Subtractive masculinity cannot correct for its losses by chipping away areas from traditional femininity, because women are already in those areas. The only way subtractive masculinity can win more space for maleness is by defining new fields as completely masculine and by keeping women out of those fields.
That last paragraph may not be very well argued because I'm sick. But I think it's important to understand that subtractive masculinity does not function symmetrically, and that on the most basic level masculinity is a more valued though more unstable characteristic than femininity. Masculinity must be fought for, must be achieved, and the basic way that happens is by teaching how men must differ from women (Don't throw like a girl! Boys don't cry!).
I can appreciate the fear subtractive definitions of masculinity could create in boys. They are horribly restricting and unfair, and ultimately impossible to comply with. I can also understand how frightening changes in gender roles can be if masculinity is only seen as What Women Do Not Do. The more areas women enter, the fewer Man-Caves there will be. Hence the need for sitcoms about The Last Man Standing. Or literal Man-Caves in suburban basements.
Finally, to the title of this post: The Wombless Women. That's the reductionist base of the subtractive masculinity. If women can do everything that men can do, what is left for men? They would be but wombless women. I think Ursula le Guin made one of her characters say this in the EarthSea (initial) trilogy, as an explanation why men's magic was superior and more highly valued than women's magic. If men didn't have that extra skill, they would be nothing but inferior women.
The reverse of that reductionist base is naturally that women are their wombs. The most extreme definitions of subtractive masculinity, those supported on the misogynistic sites, advocate allowing women no other role but that of their sexuality, and even that only when it is under total male control. History shows us examples of societies, even some current ones, where women's roles are pretty much constrained to just that minimal biological sphere.
The subtractive definition of masculinity is a truly crappy one. It must go. We could start by pointing out that many areas of human endeavor are human, not particularly male or female. We could support our sons and our daughters in finding healthy bases for self-esteem, and we could work out a concept of masculinity that is not subtractive, as well as a concept of femininity that is not self-mutilating.