Nobody seems focused on the real issue here. Freddie and Fannie were government creations, and were governed by political policy desires as well as financial realities. For example, we have to get rid of redlining. Why? It's racist and unfair. Never was the race card worse misplayed. Most default borrowers, like most Americans, are white.
The race thing was never the issue in the mortgage business, not the black thing, only the green thing. If you are poor habitually and not a good credit risk, it may be social inequities that did it to you, or it may be something else, but either way, lending you a pile of money on a government backed loan is only a good idea if you think the government is in business to play Santa Claus and pick up bad paper.
The whole scheme was a time bomb from the moment it was created. It was created for the purpose of interfering with free market forces. That's the point not to overlook, and the short take away lesson for this whole fiasco.