I certainly understand that you may not like the treatment, and I would be equally annoyed were the same thing to happen to me. But the law doesn't leave a lot of room for this sort of complaint.
If you can show that the supervisor's actions conflict with the employment policy handbook/guide, then you are entitled to file a grievance. Similarly, if you think that the supervisor had an ulterior motive for the comment, such as because he/she does not like you because of your race, color, nationality, religion, sex, age or disability, then you also have grounds for a grievance.
The point is that you must try to connect the supervisor's actions to some illegal conduct, as described above. If you can do this, then your grievance is valid and the supervisor can be sanctioned for his/her conduct towards you. Otherwise the grievance is invalid, and it will go nowhere.
I realize that your complaint here is that you were insulted in front of others, and that you didn't deserve this treatment. Unfortunately, the law generally requires more to create an unlawful act by the supervisor. So, try to think about whether or not the supervisor's actions were motivated by some other underlying discriminating motive.
Or, if you can find a rule in your employment guide that prohibits the supervisor's conduct, then you can file a grievance based solely on that.
Hope this helps.
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