"Extreme" seems an overstatement, and I don't think it's necessarily the main motivator for a lot of people that are anti-nuclear. Many don't like it because they believe large-scale power sources supplied and run by (or inevitably being a source of profit for) mega-corporations are a bad idea in general. Others because there are genuine environmental consequences to and risks with uranium mining and storage of radioactive waste that we don't have complete solutions for, even if by almost any measure those consequences are less serious than they are for fossil fuel extraction and consequence GHG emissions. And others because they're skeptical it can scale up quickly and economically enough to reach necessary emissions targets (I have one foot in that camp, at least for my own country). Ultimately I think increased nuclear power will be accepted as a "necessary evil" or "least worst" solution in most developed countries, though it's hard to see it happening here in Australia, despite the fact we supply much of the world's uranium (*) and arguably have a fair number of appropriate options for waste storage.

* actually we have almost 30% of known viable resources, but only contribute 8% or 9% of the world total supply currently, producing less than a 5th of Kazakhstan, by far the most prolific supplier.