He used his free speech to say something stupid in public. His employer fired him.
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So who gets to define what is stupid and exact punishment for legally permitted speech? The rich and powerful? America’s little guys need to be able to exercise lawful speech without losing their jobs at the whim of unelected people.
He worked for a private employer. The conditions of his employment are between he and his employer; nobody else.
Yes the rich and powerful do aka their employers. It’s up to the individual to learn how to conduct himself in public.
If he can’t then he needs to work somewhere else.