I'm an improv student (though it's been years since I've taken a class) and I've never coached. This is my opinion but I've got no illusions about how much I know.



I think it helps to remember that people say stupid and offensive shit because they literally do not understand what's stupid or offensive about it. When they get called out, it feels like receiving an electric shock for accidentally saying the secret word. They conclude, reasonably, that the best strategy is to simply remember those words and avoid them. And that's why so many people feel like it is censorship.



The question in the title of your post is "How do you call out sexist/racist/homophobic shit in rehearsal/practice/classes?" My guess is that you're probably doing as good a job as anybody. The problem is that calling out has severe limitations in what it can accomplish. It feels bad for everybody involved. It puts the offender on the defensive and makes him feel like a victim. I'm not saying you shouldn't do it—it's important and you should—but you should accept that it won't do much.



Improv was instrumental in helping me (a straight, cis-gendered, functionally-white guy) learn by adopting other perspectives and thinking through what it might be like to be, for example, a woman on a date in a restaurant. Granted, most scenes did not deal with the threat of my drink being roofied, but it got my head in a space that affected how I would subsequently read about those experiences.



My suggestion is that you confront these issues by working them into exercises. If I told you I was frustrated with my students' object work, but all I did was wait for bad object work to happen and then called it out, you would probably tell me to run some scenes where the students were required to do a lot of object work, then give them notes about it.



How does that translate to playing stereotypes and saying offensive shit? (Again, I acknowledge I'm playing armchair quarterback right now.) I'd look for ways to adapt exercises so that players were forced to play, for example, a gay character. It wouldn't even have to be the focus of the whole exercise, just something you throw into existing ones. It could be a simple as changing up how you endow characters at the top of a scene; instead of "parent and teacher" you could say "a gay parent and a straight teacher". And then give notes as you would for any scene, on whether their choices made sense for that character. Did they make choices that served the scene and responded to their scene partner? Or did they dive into a stereotype? Did they make the scene all about being gay?



I'm not claiming this would be painless. But at least it would be a way to explore these topics without being reactive. It would also help illustrate why playing stereotypes is not "funny except it offends people", but rather that it makes for bad, cheap, stupid improv, too.



I hope you don't stop teaching and I hope you find a way to deal with this shit in a way that doesn't sap all of your joy. I don't know if you have a responsibility to educate them on this stuff, but you clearly want to do something about it, and the world is better for your caring.