Yes, they should be left free to roam around Fukishima after causing so much damage because it is not their fault they have become radioactive. It is the fault of human beings for creating such buildings that could possible release radioactive chemicals into the world. They should be free to live.
The radioactive wild boars are causing expensive damage to agriculture in the area. So, are they growing crops on radioactive ground and then eating them? If so the farmers don't appear too worried about the radioactivity so why can't they cull the boar. There seems to be an anomaly in this story or have I missed something...Doesn't seem to be doing the boars any harm, being radioactive.
Though the radioactivity does not seem to be affecting the health of the boars, it is causing massive damage to the surrounding areas. The boars are eating the crops and reproducing, gaining population. As they continue to reproduce, there is more and more flesh needing to be disposed of as this meat can not be eaten or used to feed any other animals.
Officials that work with nature and the environment have been culling harmful populations of animals for many years. The boars have caused a lot of damage in this area. There is no reason that they shouldn't cull the population. It would keep people safer and would also protect the environment and the local structures.