This is Samuel and I will discuss this and provide you information in this regard.
I am sorry to hear of this situation.
If the insults are directed at you because of your race, religion, age, gender, national origin or a disability then you could have a basis for a discrimination
lawsuit and should consider filing a complaint with the EEOC
Otherwise, it is unfortunate, but there are no laws that regulate general "rudeness" by an employer or a co worker.
Anyone can be terminated for any reason that is not based on one of the above discrimination factors.
I suggest, that you could begin with the manager's superior or your HR and tell them that you are feeling harassed and you need to have a mediation to figure out why.
Please note that I can only provide information for what you ask. In that regard, if you have other questions or need clarification, please let me know here. Otherwise, I would appreciate a Positive Rating as that is how I get credit for my time.