on moral grounds
Due to reasons stemming from or relating to one's own personal moral or ethical principles. I wish you all the best, but on moral grounds I cannot be associated with your campaign any longer. The religious group has made a formal complaint to the broadcast regulator on moral grounds, claiming that the program in question promotes violence against members of their faith.
on moral grounds
considering reasons of morality. He complained about the television program on moral gounds. There was too much ridicule of his religion.