@PennyNow assume that you had a male nurse whose co-workers consistently called him by a female name (not his own). He has made it clear that this is unwelcome and offensive. He has asked them to stop and they continue to do so.
What you have described is man whose colleagues are jerks, not a title seven violation. They may or may not be in violation of a company policy but the law requires unwelcome sexual advances, requests for sexual favors, or other verbal or physical conduct of a sexual nature for a given behavior to qualify as sexual harassment.
Furthermore the situations being compared are not the same. In the example you give a man is bullied by his colleagues, who address him with a name that is not his. But that is different than a situation where one individual makes a claim (that they are a certain gender) and those around them do not believe their claim and elect to not behave as if it is true.
That is clear cut workplace bullying and sexual harassment and practically any HR officer would agree with that.
The opinions of a human resources department are not relevant.