The Arkenstone, specifically, appeared to affect dwarves the way that the Nauglamir with the Silmaril did - driving them to violent greed. (Although the results were even worse in the case of the Nauglamir; but then the Silmarils are the greatest treasures in the history of Middle-Earth.) But it may just be their general greed for treasure.
Really, despite the simplistic black-and-white morality (literally, unfortunately) of LOTR itself, the races of Middle-Earth as portrayed by Tolkien are all variable, capable of both good and evil, and overall "neutral."