Ursula K. Le Guin isn't a man-hater. Far from it. But she did need to find a way to describe the negative aspects of certain types of men to whom she was referring, without naming names. That's where personification comes in.

She writes:

Why should a free woman with a college education either fight Machoman or serve him? Why should she live her life on his terms? (52-53)

She's not alluding to one man in particular. Or even a specific group of men. But she's singling out the men that prioritize the rational, positive, competitive aspects of life that are in direct contrast to the strengths of women. It's like she needed a scapegoat, and by naming him Machoman we can be clear that she's not referring to any one man, but a quality of men in general.

She also names the Warrior, which is either the same thing as Machoman, or Machoman on steroids:

All that the Warrior denies and refuses is left to us and the men who share it with us and therefore, like us, can't play doctor, only nurse… (57)

Again, she's naming a quality; personifying a negative aspect of men, which makes it easier for her to make a point without being derogatory.

This also helps to tie together some of her imagery. Early in the speech, she says,

The war-games world wasn't made by us or for us; we can't even breathe the air there without masks. And if you put the mask on you'll have a hard time getting it off. (46-47)

Guess who can probably breathe the air in a war-games world? Yeah, we would've guessed the Warrior, too.