It's exactly like the theory of the ether. It was the fleshing-out of that theory that made physicists doubt its veracity - a substance must permeate all space,

It's exactly like the theory of the ether. It was the fleshing-out of that theory that made physicists doubt its veracity - a substance must permeate all space, be more rigid than steel yet not impede planets orbiting the sun? Really? The Michelson-Morley experiment put the final nail in ether's coffin - but there were already a number of nails. On the upside, it led to great physics! Let's hope we'll be able to say the same for Dark Matter.