That is the boss' decision. And that right should be respected. You don't get to come into someone's company , behave like you own the place and then tell him/her who they can and cannot fire. If I found out that my boss didn't like a certain trait of mine,or even my ethnicity, he/she doesn't need to fire me. I'd resign myself. Who wants to remain in a company and have a cold shoulder relationship with a boss who doesn't like you every single day anyway? If somebody was fired just because someone overheard they said that they don't agree with homosexuality, you would be okay with it wouldn't you? Yup,that's what I thought. Shows your double standard.
And before you start saying "what if it was a Black or Jew who got fired" which you like to say so much,all I can say is no Black or Jew would want to remain in the company even if the boss had a change of heart. The relationship is already strained.