I'm totally cool with whatever people want to do in bed. We all know that.
But I, personally, have no interest in strapping on a dildo and 'doing' a guy. There's no titillation in that for me. Not mentally and certainly not physically. Therefore, if the situation were that I didn't want to have anal sex, then we just wouldn't be having anal sex. I totally support that choice being the prerogative of the woman and a non-negotiable one if she chooses. It's a particularly invasive act emotionally and otherwise.