Once upon a time I worked for the government on assessing the safety of nuclear power stations, and I was involved at the highest level when a significant decision was made about the future of Sellafield (the THORP plant) - I even received a congratulatory message from John Major about the quality of my briefing for his PM Questions (boast!). One of the take-away facts from then is that most people are incredibly superstitious about radiation. The truth is that we are exposed to radiation all the time and, without it, there would be much less evolution over time. If memory serves, the UK regulatory system was much tougher on the nuclear industry than it was on, eg, the coal and fertiliser industries which also generated significant quantities of radiation - indeed, I remember being told that more radioactivity in the Irish Sea came from a fertiliser plant in Cumbria than actually came from Sellafield!
Which is not to say that nuclear power is the answer to all our problems. The principal case against it is economic, both in the medium term (it needs to be subsidised during operations) and especially in the longer term (what to do with nuclear waste). It also locks us into a centralised structure of power generation, which is much less resilient than a dispersed and localised pattern of power generation which I suspect is our future. I think there are interesting possibilities for some measure of nuclear power - eg the Thorium cycle and pebble-bed reactors - but it is probably too late now, not least because after Fukushima - in many ways an incredible testimony to the SAFETY of nuclear power! - the bar of public opinion is set so much higher.
Monbiot seems to have finally grasped two things - that radiation is nowhere near as dangerous as it is often made out to be (see this excellent graphic by xkcd), and also that much of the advocacy in the green movement is driven by emotion and superstition. I look forward to him seeing the light on SOME aspects of agw...