"Human kindness has never weakened the stamina or softened the fiber of a free people. A nation does not have to be cruel to be tough."
Why would it be okay to allow a restriction to marriage when the attraction is based on sex but wrong to make such a restriction when the attraction is based on race? The fact that a man and a woman can make a baby cannot be the answer since every state allows opposite sex couples that cannot have children together to marry regardless of such an inability.
You are not the ultimate authority on what types of relationships are right and wrong.
"A woman is like a teabag, you never know how strong she is until she gets in hot water." - Eleanor Roosevelt
Keep your religion out of other people's marriages.