The boss doesn't approve of the person you love and wants you gone because you are an abomination to him/her/them.
So what is really going on here? You don't become less valuable or less talented because you got married. Why does your boss have to approve of or even like your spouse? Heck there are some couples that one of is my cuppa tea and the other of isn't. But I wouldn't fire him/her because of that as long as the job I need done is being done well what the he** business is it of mine? How does that affect my life? I don't get it.