I agree with LtEve. Plenty of conservationists shoot animals (deer, elks etc) to prevent the sickness and starvation that results from overpopulation.
It is the kind of cull that would normally be performed by predators like wolves (and humans!) but since humans are the only predator left in this country they get to do the job.
I breed rare tropical fish for conservation (because of damage to natural habitats). If I just let all the fry grow up every month, the water would be fouled through overcrowding and they would all die in a nasty way. I also make sure to get rid of any deformed or sickly fry that would be picked off by predators in the wild. If I didn't do this job the fish I breed would be useless and I would risk doing more harm than good. (The alternative would be to keep predatory fish, but in the limited confines of the aquarium it isn't possible to do this in a controlled and humane fashion.)
Prince Charles is not giving mixed messages: he has never said that he is against poaching because he can't bear the thought of killing the fluffy animals.
He is against poaching because it is uncontrolled and carries a serious risk of the extinction of species. Not to mention the fact that there are plenty of non-human predators in Africa to do the job.
The boar is not an animal at the risk of extinction and all boar kills in this country will be carried out by licensed people in a controlled fashion.