This whole debate amazes me. To me it all boils down to a simple question:
What right have you or I and more importnatly the State, to tell anyone who they should love, sleep with or make a commitment to?
Providing those involved are consenting adults it is nobodies business but their own. If our society is so fragile, that it will begin to crumble the moment two same sex people Marry, then quite frankly it's not worth saving.
The world as whole would be a much better place if people spend more time thinking about their own actions and associated consequences. as opposed to those of others.
EDIT: Actions are more powerful than words. If you want to the world to be a more moral, better place. Live a more moral life youself, rather than focus on the immorality (as you perceive it) of other.