Yeah, I was afraid that might come up. I've forgotten, if I ever knew, what your husband's surname is. But if I wanted to, I might use Mick even if the surname was really Irish sounding, like, Murdoch or Flanagan or O'Malley. Co-opt it the way they did with "queer." In the US I think there is no reason anymore to marginalize the Irish; being Irish is cool. No insults could stick. In the UK it might be different, I dunno. Anyway you'd have to really love Michael, and if he seemed like a Mac he'd be one, and if he seemed like a Mick he'd be one - I don't think it's likely you can plan it.