Define Sanctity

I'm not often a soap box stander oner, but today I'm going to be. Just for a quick secy. Bear with me.

Everyone once in a while, when I need a break from work, I indulge in a hint of the Tyra Show. Yesterday's episode was about open relationships, and its been bothering me since I saw it.

There were these four people, right? The two in the middle are married. To each other. The girl on the right is the husband's "lover." He also has a girlfriend. The guy on the left is (I missed the beginning, but I think) the wife's boyfriend, who the husband claims to love as his brother. Did I mention the wife is bisexual? The husband and the wife have children who have relationships with all of the characters in this story.

I don't know. I just feel like there's something wrong with all of this. These people are allowed to be married, and have all these other flings and relationships and lord knows what. However, people who have been in loving, committed, monogamous relationships for years upon years with someone of the same sex are not allowed to get married because, according to some religious and political leaders, they will destroy the sanctity of marriage.

So, define sanctity. Because I obviously don't understand.