I think it's important to avoid falling into the ethnocentric trap of assuming that a "good guy" within an alien civilization is someone whose values are exactly like ours/the Federation's. Gorkon didn't make peace with the UFP because he loved peace for its own sake, but because he was smart enough to recognize that alliance was the best strategy for his nation's survival and prosperity at that particular point. Basically he was living up to the proverb "Only a fool fights in a burning house" -- with Praxis destroyed and Qo'noS's ecosystem in danger of total collapse, the Empire's survival was at stake (since the collapse of the center of power typically results in the dissolution of an empire), and so they had to focus on survival rather than continue with business as usual, and if the Federation was willing to help them survive, it was just good sense to accept their help. But in different circumstances, if he felt the Klingon Empire's political and economic prosperity were best served by going to war with the Federation, Gorkon would probably have gone to war. Because by the standards of his culture, war is not intrinsically a bad thing, at least so long as there's something useful to be gained from it.
Heck, by Klingon standards, someone who loves peace for its own sake even when it's against the Empire's political or economic interests would probably be considered "sinister."