engine:
I can see the point that it's a bit silly for a player to be bothered by what a character in a game is doing, as long as rules are being followed.
(Note: this isn't directed at engine, but this quote frames a thought I was having well)
The idea that "IC is just IC" is possibly one of the most insidiously destructive things in the tabletop gaming hobby. It's an attitude that has left many people (especially female and minority people) feeling like they're not welcome. Flat-out offensive actions done "only IC" are still offensive. Being a royal jerk to the other players is still being a royal jerk. Diving in to offensive content (while remaining within the RPOL rules, of course), is still diving into offensive content.
If your character is a racist, an over-the-top stereotype, and/or misogynist to the point that I'm personally offended, you can bet that I'm going to say something to the GM and if it doesn't drop to a level I'm comfortable with, I'm going to walk. And while that is an easy example (and annoyingly common in RL gaming circles), it doesn't have to be so straightforward. Say I just lost a loved one to cancer... I'd probably really rather we didn't play out a storyline that's all about someone dying of cancer (though I might be open to a "cure cancer" story).
Being bothered by stuff isn't a bad thing. Saying something about it isn't a bad thing. Gaming is a social experience, and some social courtesy is owed to everyone else at the table, virtual or not. If someone's child just died you don't go making "dead baby" jokes around them. If you had no idea, that's fair, but if you're asked to stop because it's really bothering someone, you stop. That's your requirement as a human being.
If you somehow think that it being part of an RPG lets you gleefully push all of someone's buttons and offend them, then I won't be gaming with you. Being "in game" isn't an excuse.
Now, if you're running a game that's going to deal with some tough themes like that and you make it clear, from the very start, that it's part of the game, that's a bit different. Giving people warning can blunt the sting of the material and you'll have many people that might have been sensitive self-select out.