I read your letter and I really felt for you up until the last sentence. I'm surprised the employee actually left the building to bring the order out (even though it was the wrong item in the bag). What I don't understand is, at what level does "speaking loud" become "yelling"? Is there a decibel range or is it up to the perception of the people involved.

What saddens me is the race card being played, which the person shouldn't have done, I agree, but sometimes when people are spoken loudly at, they feel defensive and will lash back with the first thing that comes to mind. The employee gave you an apology of sorts, face to face, when he handed you your food.

I just think maybe emotions were high, both sides were angry and on their last nerve. Perhaps wait for the anger to subside and re-write the complaint or speak to another manager at the store, the one in the photo. It may help diffuse the situation if you don't have to confront each other. And maybe the problem can be resolved. Sometimes all it takes is a little time.
I really don't see anything rising to the level of litigation.

Wish you luck and let us know how things work out!!