Men are numbed to this because of a very useful and exploited element the masculine dynamic. It's the male double standard. Feminized society very effectively conditions men to 'do anything for love' and put up with every inconsistency and contradiction their mother's, sisters, girlfriends, wives, etc. behaviors and motives. This is called feminine perogative, or in other words, a woman always reserves the right to change her mind and never be held accountable (or as accountable as a male in a similar situation) for her decisions. Men of any social value cannot enjoy this same luxury and retain respectability. It is a masculine imperative that man be resolute, confident and decisive in order to be considered "men."
Feminized society uses this dynamic to a supreme advantage in many different ways. The easiest illustration however is the subtle and overt acceptability of male bashing in popular culture. For instance a woman could wear a t-shirt stating "Men are Dogs, Keep them on a Leash." (yes, I've seen this) with little if any societal repercussions. In fact she'd probably be met with a few shared chuckles and a "you go girl", while if a man were to wear a similar shirt stating, "Women are B!tches, Keep them on a Leash" he'd be lucky not to have rocks thrown at him - not only by women, but other men as well. This is the degree of this acceptability that men will despise this sexism only in their own gender.
Why should it be then that men would make no response when blatantly confronted with this acceptable gender bashing when women are the perpetrators? This dynamic is directly attributable to this masculine double standard. Traditionally men are expected to "tough it out" and "put up or shut up." This is a very admirable characteristic in the traditional masculine - don't complain and get the job done. So while feminized society ridicules and devalues anything remotely resembling positive masculinity, it simultaneously expects a male to retain his silent, persevering qualities as a responsibility. As if this hadn't gone far enough, this schema also encourages men to join in their own bashing by throwing rocks at the men who have the ability to see this dynamic and posess the courage to point it out. For merely saying that things are less than equitable in this regard, he's punished by being termed a 'caveman-chauvinist' or a potential abuser by the women and men subscribing to this sexism.
Like good AFCs do, these men are motivated to debase their brothers in this dynamic in an effort to better identify with women to prove themselves "not like other guys." Guys in this mindset eagerly jump on any occasion to throw rocks at men with the courage to reveal this discrepancy, as even the hint of it allows for an opportunity of qualifying themselves to women. This effect is so pronounced that AFCs will do this even in relative anonymity or in the presence of an all male audience as an exercise in potential social proof should an eligible woman be told of it.
The AFC that will blindly maintain this dynamic will also subscribe to male subservience - such as the guy WESTCOASTER described in his initial post - since this model has been reinforced enough to condition him into this schema. In essence men are taught to hate being 'men", while still being expected to embody select, masculine characteristics that serve the purpose of their continued self-gender hatred.