The ruling was made by a tribunal which was considering the dismissal of Tony Finn from Mirfield-based British Bung Company, which makes items used by the brewing industry.
It was made by a panel of three men who made reference to their own baldness in the report. Mr Finn was fired from the company, where he had worked with an "unblemished record" in May 2021.
In a statement made to the tribunal, which was heard over six days in February and April in Sheffield, Mr Finn said: "I was working on a machine that I had to cover awaiting specialist repair. The covers were taken off, and it was apparent that Jamie King had done this.
"When I spoke to him about it, he began to call me a stupid old bald **** and threatened to ‘deck me.’ Fearful for my personal safety I retreated to the nearby office of Ady Hudson, supervisor. Jamie continued his tirade of threats and abuse at the office door. This was witnessed by Ady.”
The report said Mr King accepted he had called Mr Finn "a bald ****" and threatened to "knock him out".
Mr Finn then refused to return to work "because of circumstances of danger which he reasonably believed to be serious and imminent".
He wrote a statement to his employer using West Yorkshire Police headed paper as his son was a police officer. The company then accused him of trying to intimidate them and fired him.
The panel's judgement said: "In our judgment, there is a connection between the word 'bald' on the one hand and the protected characteristic of sex on the other. Miss Churchhouse was right to submit that women as well as men may be bald. However, as all three members of the Tribunal will vouchsafe, baldness is much more prevalent in men than women. We find it to be inherently related to sex."
The judgement also referred to a previous case where a woman had been sexually discriminated against when a comment was made to her about the size of her breasts.
It went on: "It may be thought that such a remark is inherently related to sex. However, a similar comment may be made to men with the condition of gynaecomastia.
"Upon Miss Churchhouse’s analysis, therefore, were a complaint of harassment related to sex to be brought today by an individual in the position of the claimant in the Insitu case, it would fail upon the basis that it is possible for men with that medical condition to be subjected to the same remark (just as bald women may be subject to comments such as those made by Mr King) albeit that far more women than men will be liable to such harassing treatment."
The panel will meet to decide on compenation for Mr Finn after he won his claim for unfair dismissal, wrongful dismissal and being subjected to sex harassment.