How in gods name did Muslims turn a specific decree for Muhammad's wives in to a general pronouncement? sounds more like a pack of unsophisticated half witts pulling on straws to justify segregation
It's called preventing the means, or sadd al dhara'i. It basically means that the ulamaa have given themselves the permission to allow one another to make up ever more restrictive rules for the society - mainly for women, of course - in order to (theoretically) prevent people from being in situations where they would be tempted to engage in the activity that allah declared haram. In this case, zina. It gives them the double advantage of exercising a lot of control over society and giving them more tools that they can use to ostracize people who challenge or question them or the ruling powers. They say that only allah and, in some circumstances, the prophet, can declare something haram, when in fact the ulamaa have declared many more things haram by default with the category of 'makruh,' which has become de facto haram.
So zina is haram. The prophet said a man and woman shouldn't be alone together. The ulamaa go further and say they can't shake hands or look one another in the face or speak to one another or work together or sit in mixed gender gatherings (and then, to further complicate things, some others come along and say that some of those things are okay). They say that women can't pray in the same room as men or in the masjid at all. Because all of that could lead one man and one woman to get it on without getting married first.
You can see the same concept at work in the obsessive ban on products with pork or alcohol byproducts in them. For example, some lotions or perfumes with miniscule amounts of ethyl alcohol b/c some mullah somewhere says that if someone consumed enough of it, they *could maybe* get drunk on it. You know, provided they didn't fall over dead from toxic poisoning first.
Topic: Separation