Documentation of diagnosis would definitely help, but in a right to work state it only goes so far. Meaning, don’t stop at the diagnosis documentation - start documenting when this occurs, what occurred, who was involved, and who witnessed. Save any written communications that might corroborate or support the toxic environment. They can still fire you for no reason, but any sort of paper trail/history can help get proper advice from a lawyer if need be (even in right to work states, harassment can get them in major trouble). On another note - people like this are awful. They just make it worse with such comments/actions. I’ve always wondered how they would react if confronted with that fact. Just, dead stare “you know you’re only making it worse, right?” Might be more effective coming from someone else who witnesses the whole thing, who knows. They just don’t understand the full depth of consequences of being an AH. And they often don’t stop that behavior based on age - my own aunt made fun of my speech impediments when I was a child, and they’ve never even been severe. But they sure as hell got worse when someone like her pointed them out.