"The problem is incremental ism."
That is an argument for politically correct thinking. That a child must - for example - be suspended for having a pen knife on a key chain he had not though anything about because it is a tool. Because if you allow that - God forbid - then next he will bring his cub scout knife to school that he uses to whittle pine box derby cars, and if that is overlooked, then next a toy gun, than a BB gun, than an Uzi.
We have been blasting the irrationality of P.C. intolerance that throws common sense out the window.
The stipulated facts are: They are not blood relatives. They love each other. They are making babies who need respect from their peers and protections engendered from the anchor contract of a family known as marriage. How you could come up with a wild idea that unless we don't let them live in sin the world will end is beyond my comprehension.
That's what they all say. NAMBLA - pedophile homosexuals say they "love" their victims, homos getting married in SF, incests, polygamists.
If adoption makes one legally a sibling, why can't real siblings then marry? Wouldn't that be the next step? According to law, adopted children are equal to legitimate children.
There's strange people in this world. I understand your "non blood" argument, but doors would be opened that should really remain shut.