So... your preferred alternative is to not judge a moral code by its results??? Then why should we even care?
The problem is that objectivism doesn't claim to be simply useful, it claims to be objectively true in its principles. Judge moral codes by their outcomes all you like, but that's a fundamentally utilitarian approach, not an objectivist approach. If the principles of objectivism are objectively true, we ought to be able to see them proven rationally, not by simply appealing to the consequences. Appealing to the consequences in trying to demonstrate the usefulness of a thing is perfectly appropriate. Appealing to the consequences in trying to prove the truth of a thing is, as you must know, a logical fallacy.