This is more of a question about what qualifies as a moral judgment. It's possible to make moral judgments (under one definition) from the outside about other systems of morality or other people's utility functions, e.g. "According to Christianity, masturbation is a sin" doesn't motivate you to stop masturbating unless you firmly believe in Christianity, and "According to Bob's utility function, he should donate more to charity" needn't motivate you to donate more to charity. On the other hand, it's impossible to believe "According to my moral system, I should do X" and not think X is the right thing for you to do.