No one was offended that two corporations could portray themselves as engaging in the sacred institution of marriage. Marriage is considered a sacred institution and yet people who don't know each other can engage in it in front of 23 million people with virtually no protest. California, a state many people think of as tolerant, crunchy, and free, is about to vote on a state ballot proposition which would recognize marriage as valid only if it exists between a man and a woman. It's called the Sanctity of marriage act. It seems to me that marriage between people of the same sex is only a threat to individuals who don't feel comfortable around gay people.
Marriage is a percieved bond between two adults.
More importantly marriage is a social contract between adults which is recognized by the state. We can describe male or female characteristics both physically and mentally. I know masculine women who are flat chested, have short hair, and exhibit virtually no common feminine characteristics. I know men who are so effeminate, if I was blind I would guess that they were female. Physically some percentage of people have characteristics of both male and female genitals.