Pragmatic justification: Some linguistic or discursive form or an assumption is pragmatically justified in so far as there is adequate reason to go on engaging in a practice that exhibits that form or that makes that assumption.

I read somewhere that moral realism is not a required assumption in moral practice. Because of this, it is not pragmatically justified. Because there is a possibility of carrying on with a useful moral practice without making the assumption of moral realism, moral realism is thus not pragmatically justified.

My QUESTION: Why can't moral realism be pragmatically justified? It seems this all assumes moral realism can only be pragmatically justified if it is a necessary or indispensable assumption in moral practice. I'm not quite understanding why it can't be the case that moral realism IS pragmatically justified even if it is possible for moral practice to not require it as an assumption.