Controversy time. This post will likely generate an argument of two in the future, but I feel it's important to take a stand. I fully support marriage between two people of the same gender.
The flippant explanation would be that I'm not a hateful bigot, but that reasoning wouldn't take me anywhere, as true as it is. Marriage itself is a contract between two people; the important part is the relationship itself. For those who would argue that there can't be true love between two people of the same gender, I challenge them to prove that true love between any two people. Love itself is internal; external proof comes from our behavior that is evident between any two that care for each other.
I hate to say it, as true as it is, but much, if not most of the opposition to same sex marriage comes from religion. Just about every holy book seems to be against the concept. Odd how these same holy books were written by people who 'knew' that the Earth was flat and the center of existence.
I believe that there is room for infinite diversity in infinite combinations. I believe in inclusiveness, not exclusiveness. I believe in equality for everyone. Deal with it.