I'd argue that calling someone a MILF in the workplace is already harassment. The problem with passively sitting by is that it can introduce more problems down

I'd argue that calling someone a MILF in the workplace is already harassment. The problem with passively sitting by is that it can introduce more problems down the road because someone can claim that you passively sat by and fostered a hostile work environment. The harasser also has more credence if you only confront him until he does something else because at that point he can claim he didn't know it was a problem.