The problem is that people also compare this with outdated designs for coal plants.
There are much cleaner modern coal plants with filters.
Still coal is dirty and dangerous.
In the nuclear industry you have new designs. But this does not solve the basic problems:
* mining of Uranium is dirty
* you need to transport dangerous material
* nuclear weapons can be produced
* reprocessing is extremely dirty
* storage is unsolved
* it promotes large corporations with all problems (corruption, ...)
* a society needs to be sufficiently advanced to handle the risk (i.e. better than Japan, the Soviet Union, or the US)
* the capital costs are large, needs to financed by the government
Plus with the new reactors you get interesting new dangers. Ever heard of 'stuxnet'? There are now viruses and attacks against nuclear facilities based on computer viruses.