Love me, defend me.

   For better or for worse, for richer, for poorer, in sickness and in health, to love and to cherish, to defend? We make a promise to stand beside one person for the rest of our natural lives. We promise to be there when times are hard and to never stop loving them, but what about defending them?
   It can be especially tricky if it involves someone that has been more involved in your partner's life than they have been in your life. You feel like you want to protect them but you might be afraid to cross that boundary. While dealing with people from your life may also pose a challenge.
   I'd love to hear your thoughts about this. When do you defend your spouse? And with whom? Furthermore should you defend even when they are wrong?