I think he is saying nobody on the left is complaining about how it is mandatory for men, but voluntary for women making it a sexist policy. People might be complaining about it is happening overall, but not about the sexist part.
Every leftist org ive interacted with places cis-males basically lower status than anyone else. Ive even had that used around me as a slur, almost like they dont really understand.
Attacking people just because they are cis- and AMAB (assigned male as birth) isn't bad. Its your actions that determine good or bad.
And, throwing men into a potential meat grinder of war is unethical. Frankly, it should all be actual volunteer, and not this doublespeak shit of voluntarily required.
Theres also this now public problem. Do trans-women count as men or women? And do trans-men count as men or women? The best answer is "volunteer". But governments are weird, especially the conservative/fascist adjacent ones.
Seems to be that whether it's mandatory or voluntary is based on one's sex, not on any sort of identity.
Which makes sense otherwise a lot of males would be able to opt out by claiming that they are women in their minds or souls or in enactment of gendered stereotypes or whatever it could possibly mean to identify as the opposite sex.
Men are the ones used as cannon fodder mostly because from a reproductive point of view they are more disposable. They also tend to be physically stronger so are more suited to many combat roles that require raw strength.