My daughter's dad uses the word sissy with her when she is being what I call a double baby. I don't…

My daughter's dad uses the word sissy with her when she is being what I call a double baby. I don't really care because he says it in a joking way "don't talk like a sissy, use your words" and she's a girl but if we're having a boy I don't know how I'd feel about him using that word with him even if it is joking.