I got asked, "Can't you envision a post apocalypse that doesn't turn into a rape-ridden hellhole? Are you so limited that you can't believe men and women might work together to survive?"
I looked at my questioner. "Serbia. Rwanda. Pitcairn Island. The Beta Boys. MRAs. And every shooter who did it because 'he didn't have a girlfriend.' I believe some men and women will work together. I believe more men will revert to might makes right and start noticing they have 5 inches of height, 30% more upper body strength and a lot more aggression."
And they thought I was the sad one.
Another week, another campus shooting by a man who was upset that women would not acquiesce sexually as he thought they should. (Shakesville has a good article listing these) More attacks on women's bodily autonomy and health care from terrorists on the street and from our lawmakers.
All I have to do is look and I see a lot of men who don't think women are people, but rather objects for their comfort.
An apocalypse won't change this.
If anything, it will reinforce it.
In Stephen King's The Stand, the character of Fran comes to realize she is not protected by laws and society any more. The only thing standing between her pregnant self and the depredations of the lawless is her own gun and possibly a man of good will. "Women got pregnant and a pregnant woman was a vulnerable human being."
So yes, when I write post-apocalypses, there are going to be horrible people. There are going to be people who set up groups designed to oppress other people. Unless the group has strong female leaders, it will revert right back to male dominance and possibly chattel within a generation or two.
There's a scene in Brian Keene's Dead Sea, where the survivors on a boat are discussing how to negotiate with an oil rig crew. One suggests offering the women as trade goods. A couple agree with him but the captain shuts that down fast.
If one person is thinking like that within less than a month of civilization being gone, more will follow the longer the crisis goes on.
Even in my own post-apoc, the circuit-riding bikers sell women between settlements and get a higher price for pregnant ones. In my zombie apoc, the lady trucker mentions some places are using women as currency.
And because I follow the news and reality and I see the pushback and hate, THAT'S why I write post-apocs as horrible places. Even without the zombies.