There is a lot of theft and murder in my games. There is never any on-screen torture, though it might be implied. There is categorically no rape or sexual abuse, and indeed that would be a red-line for me: if you think that kind of thing is fair game as subject matter at the table, then we're probably not going to get along.
Why is it that most people are okay with depictions of looting, violence, arson and the like in games (and indeed often see such activities as the most enjoyable element of the entire enterprise) but not rape? To extend the question a little further: why is that we do not see anything particularly concerning about cinema audiences getting excited about watching, say, swathes of Zulu warriors being mown down by Welsh riflemen gleefully singing 'Men of Harlech' while being egged on by Michael Caine, and yet we would (quite rightly, for reasons which we will come to) be very worried indeed at the prospect of people being entertained by sexual violence?
The answer I think is relatively straightforward, though not often articulated. It's that while we can envisage circumstances in which violence, or for that matter theft, is morally ambivalent or even justified, rape is simply always and unambiguously a moral enormity. It is absolutely right that people should be squeamish about it: it is disgusting and horrible and there is no situation in which it could possible be deemed as having any redeeming features whatsoever.
This is probably also why torture occupies a bit of a grey zone. I'm not persuaded that torture is ever justifiable even in the classic 'ticking timebomb' scenario. But I recognise that there is some fuzziness about that and there are some people who would take the opposing view. So while I feel a bit uncomfortable with the idea of PCs torturing an orc merely to find out where the tribe's treasure is hidden or whatever, I couldn't envisage imposing a blanket ban. Instead, in that kind of scenario I have usually accepted a statement to the effect of 'we torture the orc' and then moved on. (Thankfully, it doesn't often come up.)
I was intrigued to discover that the 'yoof' of today have come up with a way of systematising what is and is not permitted, and in what form, in a game, with the concept of 'lines and veils'. The idea here, at least as I understand it, is that a 'line' precludes a particular thing from cropping up during play entirely, whereas a 'veil' is something that can happen, but only ever, as it were, 'off-screen'. As is often the case when mainstream gamer nerds try to parse their way through normal human interactions the concept is always framed in an intensely cringeworthy way - like Martians trying to explain to each other how to get along with earthlings - but this is one innovation I can see some merit in. Sexual violence is a line. Torture is a veil. That works for me: I get it.