If you take a propane torch and warm the entire rotor up to about 175 degrees, it will come right off.

Don't make the mistake of heating it near the hub. You need to heat the entire disc, evenly, so that the whole slab of metal reaches about 175 degrees or so. This might take you 15 minutes because it is a decent piece of iron. You should get an expansion of the hub diameter of about .001 at this temperature (100 degree rise above ambient) which should be sufficient to break any bonds that the disc has with the hub.

Much easier than smashing the thing to death.