I fail to see how someone can seriously claim to feel insulted by being called “cishet”. It's just a description of what they are. I mean, it's almost a scientific designation. It's like someone insisting on not being called “human being” because they allegedly feel insulted by it. It's just a ridiculous stance to have, I think. And I'm curious, what would people who feel insulted by “cisgender heterosexual” want to be called? It's a descriptor that was explicitly introduced to avoid calling their gender or sexuality “normal” or anything else othering LGBTQ+ folks.