There's a guy on YouTube who does communications skills (Dan O'Connor) and he says simply standing up and walking out is a powerful answer. I agree. I just finished a Stoicism class in anger management and in stoicism there isn't really such a thing as "justifiable anger" - anger is a negative emotion and needs to be processed rather than expressed. You're supposed to pause, process (for a day or two if needed), then respond (as opposed to react) when you are calm. Processing can include spending time with nature, or writing things out.

To me, standing up for oneself means being assertive, not aggressive, and it's too easy to fall into the latter if you are angry.

I just finished a course in Stoicism, a philosophy that has helped me a lot. It helps in dealing with people and managing my own life. If interested check out Ryan Holiday - on Youtube or he has published several books about Stoicism. I have no affiliation or connection with either Dan O'Connor or Ryan Holiday.