It's just that the scenes involving Black Mask are really the only parts of the run that people seem to post (me included, though I aim to remedy that). And since people on the internet seem to judge a comic based solely on a couple of out of context pages that are posted, for good or bad, they can decide that the whole of the Brubaker run is squashed hookers, enforced cannibalism and implict sexism.
The reason why these bad things happened to the characters was A) to get the plot to progress, add tension and character development etc. The fact that this was a book with a primarily female cast means that bad things are just as likely to happen to them to get the plot to move forward.
That isn't sexism, that's storytelling. Bad things happen to the male characters too. In fact Selina and Holly's girlfriend Karon are the only two who come out of the Relentless storyline (mostly) Okay. Plus if the genres so of the characters were reversed there wouldn't be the objections to it.
And B) the reason why Brubaker etc. was allowed to do those things to the chatacters was that DC told him that "they didn't care", due to the fact that they were dead (Holly and Black Mask) or just had dropped off the map (Maggie) by this point. They were characters that were related to Selina that would fill the narrative role, not Brubaker going "I need some wimmens to brutalise, mwhahahahaha!"