Environmental activists don't oppose nuclear power out of fear of radiation, they oppose it because they oppose technology, period, and for two reasons: first, because it is an artifact of man, who they hate, and second, because it is an artifact of capitalism, which they hate. There isn't actually a great deal of science behind the issue from their point of view.
Petroleum powered devices
Coal powered devices
Nuke powered devices
Hydro powered devices (let the river run free to the sea)
Wind powered devices (when the mills are in their backyard)
My prediction is that if solar power ever becomes practical they will oppose that.
Bill, I think you have hit on it. Nuclear energy is feared because it could lead to more human growth. Environmentalists who liken mankind to a cancer on the planet cannot abide a source of convenient low cost energy. They use radiation fear as a weapon to further this aim.