No one is wrong or right. Vaisnavism see God Visnu as the supreme menifest of the reality(Bramand), Saivaites sees Lord Shiva as the supreme and shaktas sees the Devi as the supreme. So, who is right? All of them, because Siva, vishnu, devi, and others are menifestation of Bramand). The ultimate reality, supreme godhood or any other name you chose to give is formless yet has many forms, is neither male nor female yet is both. So, Mahabharta is not worng Krsn can be devotee of siva and still be supreme or vice versa.
