I'm just pointing out that your use of quotation marks around the word marriage was likely equally offensive to her as her comments to you were.  That said, I haven't spoken with Jamie on this, so I may be speaking out of turn myself.  

As for disagreeing in an agreeable manner, I think always of a friend of mine who is in the Georgia State Legislature.  He and I are good friends.  We go out just the two of us to hang out, and we also hang out as families.  I cannot think of any vote he cast on a major issue this year that I agreed with.  Not a single one.  I live in his district and will vote against him in the fall.  He knows that, but guess we're still very good friends and can talk about these issues in a civil and friendly manner.  Even joke about them too.