It's an extension of their natural desire to domesticate men, who are rough and dangerous and need to be "tamed" to become useful to the weaker sex. Polite society and civilization itself are at odds with hyper-masculine aspects. There's a reason women are said to be the "keepers of civilization", because men left to their own devices acting out male instincts would just destroy it.
The healthy version of this instinct is a woman demanding that a man engage in monogamy, instead of following his libido wherever he can. It's a woman wanting the strong man to show gentleness, the adventurous man to end his wandering lifestyle and settle down. It's toning down the male characteristics that mark out men as being stronger than women, the things that reinforce a woman's weakness, the things that clash with women's "softer" desires which cause normal men to resist them.
Then there's the unhealthy extensions of this instinct. There's the women who try to belittle everything male, and eliminate every overt masculine trait of the men in their lives. There are studies that show straight women are more accepting of cross-dressing and trans-trending men, much more than men are of the same in women.
And then there's the extreme version of this instinct, the desire to see straight men as gay. There is no more emasculating thing than to be dominated by a man in the same way a woman would be. A gay man does not express sexual interest in a woman, and is therefore not a threat to her (this takes the darkest possible view of male/female interactions, treating sex-as-power as the primary definition of every relationship). And gay men exhibit female traits and behaviors, which women understand better and can manipulate more easily.
