Chlorine can kill everything if it is 'break-point' injected at a hydraulic jump, but obviously there will be pockets that take more time and effort. The important point is that the water can be dealt with far more easily, and safely than prodding the people into an insurrection. Those who have stayed behind are not the soft-haired sheep that will just give up without a wimper.
If I had this muck in my house, I wouldn't stay. But if I were the folks who were still dry, had food and water and no kids, I wouldn't leave. I don't get the mandatory evac for folks who haven't got water contamination probs in the house. Unless they're worried about skeeters and/or other airborne contagions. But still, if it's not legal, it's not legal. Where the heck is the Justice Dept?