I'm not sure it would be considered any more ok if it was the father wanting to be called by his first name, would it? I'm not sure that if you had a mother and a father not wanting to allow their children to call them mum or dad, that you'd have anyone going oh my god, not wanting to be mum, how shocking! while at the same time shrugging their shoulders and going well, be Ben if you want to be, no big deal.
I was on that thread and I must admit I did find it sad. I thought of my children and thought about telling them that I did not want them to call me mum. That they had to call me by my first name. I couldn't help thinking that a child might feel rejected by that. Not to call your parent by their first name, but the idea of being told your whole life that you cannot call them mum. I realise that's irrational and it has NOTHING to do with how much you love your child, I do get that. But the emotional part of me still reacted to the idea of a child being told no, don't call me mummy, I'm not mummy, I'm X.
However, the feminist issue is, I think (I await to be corrected on this if I have misunderstood/oversimplified the issue), that when you are a mother - that is all you are! As a woman you are defined by your roles to other people. So and so's wife, so and so's mother - and you can lose YOU in that. You become nothing more than what you are to other people, iyswim and you must take yourself to the bottom of the pile, with everyone else's needs coming before yours at all times.
Whereas a man is always him. He may be a husband, he may be a father, but he is always HIM.
And the prize for most inarticulate post goes to hecate 