I accept that the definitions of "men" and "women" have evolved to the point where it's about more than what kind of genitalia one has, but I don't necessarily believe that this was the black-and-white "right" evolution path of those definitions, and I actually think it has evolved somewhat arbitrarily.
I don't see anything worth fighting about in Manning's choice to identify as a female, but my natural inclination is to think more like PiB. I actually think that maybe it's good for there to be stiff definitions of men and women based solely on exterior biology. When you think about it, making it more complicated than that means that societal oppression has won. If a young boy likes to play with dolls, other children will no longer learn to accept that it's OK for some boys just to play with dolls-- they'll just learn that he is in fact, a girl. What if someone has interests that are more commonly associated with the opposite sex, but has no desire to change his or her biological sexual identity? They might end up being raised as the opposite sex before they ever get a chance to speak for themselves, which is just a different version of what people like Manning have struggled with.
"LIVE OR DIE, MAN??"