But we know, that some Dwarves fought along the side of Sauron in the War of the Last Alliance. Parts of every people (save the Elves, of course) fought on both sides, consequently there must be some 'evil Dwarves' in that time. And I would guess, that these Dwarves live in the East. Otherwise we surely have heard some details of it.
Actually, Sauron must have bought them with some gold......
