I oppose homosexual marriage, but I don’t see deciding original case differently if the wife took up with a man or a woman - the husband would be resentful in any case. Did he endanger her at their workplace? Did the employer fail to take action?
Notice also that the definition of “discrimination” keeps morphing. Originally, it meant getting or keeping a job or promotion. Now it means if you say you feel “uncomfortable” at work due to certain people, THAT is now “discrimination.”