The public perception of the dangers of anything radioactive is quite exaggerated, the politicians in these cases are only representing the views of their constituents. Having said that, I don't think you can reduce the argument to something as simple as salt in an ocean. Like you (almost) said, the concentrations are extremely different, particularly if something goes wrong with the containers in the millennia they are buried for.
"The public perception of the dangers of anything radioactive is quite exaggerated."
Not when you bring the timescales into account, recognize that you'd have to scale operations up massively from present levels (15,000 or so plants vs. the 436 presently operating in the world). This would mean commissioning and decommissioning about a plant per day.
Add to this questions over fuel availability (known reserves are good for about 80 years at present levels of use, 6 if used for all human energy needs), and the need to find some way for creating transport and storage fuels, and nuclear is at best a small part of a much larger energy solution.
http://xkcd.com/radiation/
Not entirely related, but an interesting read: http://en.wikipedia.org/wiki/Goi%C3%A2nia_accident