> some people -want- men and women to be interchangeable in all respects
That's a generalisation that loses all sense.
For example, you're building giant pyramids out of human corpses. Based on experiments and precise calculations, you know that you need x.y% more female corpses than male corpses, and get really angry when suppliers try to argue that men and women are equal in all respects.
Obviously, this is not the important question. We should ask questions about your activity as a whole instead.
(It might seem that my example is a bit over the top, but people around us do things that are just as bad, and with real enthusiasm.)
Gender issues are not just abstract, they are tied to problems people see in the society. It is not fashionable today to just state that someone is a swine to behave in some manner (and the answer would usually be that you are not allowed to limit anyone's freedoms), so dumb pathetic fences of bureaucratic states are used, and the talk about progress, benefits, equality, shared future, etc. floods the stage. However, you personally still either think that something is right, or that it's wrong.
During “millions of years of evolution”, in many places any woman walking alone without male relative or servant could be treated as a potential free sex toy. It was simply “evident” that anyone could try to rape her, and “everyone” knew that — men, women, kids. It was “natural”, and even the commandment about neighbour's wife could easily be seen as excluding “no one's” or “everyone's” wives, so it was even sanctioned from above. Obviously, it all stemmed from the heads of certain people, and changes introducing consequences mutated that “natural order”.
By the way, the figure of noble male saving damsel from the jerks is considered noble because... he could've joined the party, but choose not to. What a hero! Simple-minded people continue to see things the old way to this day when they expect heroines saved by the hero to have sex with him immediately. Because what are other options, really?