Nah, he is not so bad, really, if you consider the fact that the other guy had (indirectly) his lord and lover killed and he lost his dominant hand while trying to save him. Also, having sworn absolute fealty to his murdered Prince meant that he gave up his claim for the lands of his family and stood there crippled and penniless and without the family bonds that meanteverything in medieval Wales. So, he had legitimate reason to be less than forgiving.