You're right, very early on the climate was very pro-nuclear, and I should have said 30-40 years instead of 50. But when it swung the other way, it swung HARD - my statement wasn't hyperbole, most plants in that period were literally stalled out of existence by anti-nuclear groups.
I wasn't saying that there are no real concerns for safety or non-proliferation or waste disposal - I'm saying that they were so overblown by the environmentalist fringe that the projects were stopped completely due to legal hassles, and that is true.
Constantly changing regulations had something to do with it, too - these things take 10+ years to build even without opposition stall tactics, and by that time the regulations would be so completely different that the plant would require several years of modifications to be brought online. Regulations have stabilized somewhat since then, which makes building new plants or finishing abandoned ones a much more attractive prospect.