We don't cringe at the thought of stealing from old ladies because it's wrong, but rather we call it wrong to steal from old ladies because we cringe at the thought.

I think this analysis oversimplifies the fear of nihilism. For example, we punish those who steal from old ladies, because the stealing is wrong. But we don't punish everyone whose behavior makes us cringe. At least I hope not.

People who fear moral nihilism are not worried about losing control over their own behavior, they are worried about losing control over other people's behavior.