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You mentioned that you were the only black employee. While this is a useful fact, it is only legally relevant if you have some evidence to suggest that your race was actually the basis for this treatment.
The EEOC can't make claims anymore based solely on statistical evidence. There needs to be evidence of some sort to suggest a causal connection between your race and the treatment.
In this instance, you're fighting against a basis for the treatment that isn't racism....the issue of you disagreeing with your supervisor's opinion on terminating an employee. While you certainly have that right to disagree, such disagreements on staffing issues are not legally protected and an employer absolutely can hold what they consider to be an incorrect staffing choice against you. It's part of everyday business, to decide who does and does not belong in the workplace, and if that supervisor says that they do not trust your judgment based on the disagreement that can be argued to be a legitimate, non-discriminatory basis for the demotion.
Now, on the issue of hostile work environment, that claim only works if based on an illegal factor. Here though, your claim seems to have more merit as you note that you are the only one yelled at in this way. That is called disparate treatment and can force the basis for a claim.
I would contact the EEOC in your state to have them start an investigation of the treatment by the Appointing Authority.