No individual nor business can suppress freedom of speech. Only government can do that.
This is bad, but has nothing to do with any freedom, much less freedom of speech.
BTW Are you a Constitutional Scholar?
He said she mentioned it several times to him. As a former employer, I can tell you that she had no business bringing up her personal life to a fellow employee that she did not know. Her raising this issue surely gave him the justification to express his personal beliefs on it. She should have been repremanded. It is apparent that she was trying to goad him into saying something. I suspect that if she had simply mentioned it in passing one time, he likely would not have responded as he did.
“No individual nor business can suppress freedom of speech. Only government can do that.”
They can if it’s laid out specifically in writing and the employee has read the document and signed an acknowledgement.