These speak for themselves, I think.
1. rape as lazy characterisation
You want to show your villain is a Bad Man, so you have him rape a woman. You want your fluffy princess to become a feisty amazon, so you have someone rape her. No no no no no no no. Do not treat women like this, not even in fiction. And when Mr Fantasy Author responds, “that’s what it was like in the Middle Ages, you moron”, but also quite happily replies with “it’s a made-up fantasy land, you moron” when the accuracy of his Middle English has been questioned, then I would suggest that Mr Fantasy Author is the real moron. If you’re going to make shit up, don’t make up regressive sexist shit.
2. the lone gunman
Thousands have died, perhaps millions, and it’s all the fault of one man (it’s almost always a man). He deliberately gave the order, or pressed the button, that resulted in all those deaths. He’s a monster, and he acted in a vacuum, according to motives of his own. He’s not part of a political or religious movement, he’s not the general of a conquering army. He is the lone gunman, the lone psycho. Like the corporate executive, in a Hugo-shortlisted space opera, who hires gangsters to seal the exits of an asteroid city with a population of 1.5 million, and then subjects them to a fate worse than death by infecting them with an alien virus… just to see what will happen. If your plot depends on one person acting like an inhuman monster, you need to rethink your plot.
3. post-catastrophe man is an animal
Thirty years ago, we were waiting for them to drop the big one and then we’d all be scrabbling for survival among the radioactive ruins. Now it’s more likely that climate crash, or nation-state failure, will do for us. Either way, our current way of life will be toast. So, of course, once this happens the men will all run rampant, rape all the women, steal everything, and kill anyone they don’t like the look of. This, at least, is what fiction tells us. We will not try and rebuild our communities, we will not recognise that cooperation increases our chances of survival. It’s every man for himself, and the women are chattel. Of course, our present ruling classes want us to believe this – they need law and order to maintain their rule, so they want us to believe that without law and order we will turn into brainless animals. In Davide Longo’s The Last Man Standing, a middle-aged couple break into the protagonist’s house and steal all his food and clothing. Regressive, but relatively plausible. They also shit all over his furniture. Why? Why would anyone stealing food to survive also shit on their victim’s furniture? If you have characters in your post-apocalypse novel raping women and shitting on beds, do “select all”, followed by “delete”.
4. the tart with a heart
It’s not just that it’s a horrible cliché centuries past its sell-by date. Think what it says about your invented world. If prostitution exists, or even flourishes, then it is not an equal society. It is patriarchal. And that makes it sexist. Is the human race – one half of it, at least – doomed to be sexist until the heat death of the universe? Biological apologists are no better than creationists. Leave regressive crap like this where it belongs – in religious books.
5. artificial people are not people
Humanity finally manages to create a race of artificial human beings. And promptly enslaves them. No no no no no no no no no. If they’re human, they’re human. They will have the same rights as everyone else. We did the slavery thing centuries ago, it was wrong and we know it was wrong… so why would we do it again? This goes for AIs too. If it’s sentient, it’s not a tool. And if you should find yourself writing a sex slave character, take your manuscript and burn it. And do not write another word until you know better.
ETA: I have added “as lazy characterisation” to the first point as it was rightly pointed out to me that it originally read as though I felt rape should never appear in fiction, when it was my intention that its use as lazy shorthand characterisation should be avoided. Rape should be written about, and as a man I am not in a position to say otherwise. I apologise for any confusion, and take to heart everything written by Kari Sperring in her response here.