I am seriously having great problems reading this thread.
I mean, this is a joke, right? Some of you people actually are for this? This might just be the most depressing thing I've heard for a while.
Society and societal functions are naught but social manifestations of evolutionary structures. Anything that goes against the evolutionary cause will most certainly bring about the demise of any society.
Freedom is not absolute goodness, and I hope and pray for the day when people see this and see the error in their ways.
It is alarming that we even have to explain why it is not a right thing to do - let alone that there are people advocating it. All this, to me, tells that our society has sunken into deep levels of irrationality.
There's always been people in incestuous relationships. It's not like it's anything new, and humanity is still here. Big deal.